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Collaborative Statistics (MT230 - Spring

2012)

Collection Editor:

Robert Gallagher

Collaborative Statistics (MT230 - Spring

2012)

Collection Editor:

Robert Gallagher

Authors:

Susan Dean

Barbara Illowsky, Ph.D.

Online:

< http://cnx.org/content/col11403/1.1/ >

C O N N E X I O N S

Rice University, Houston, Texas

This selection and arrangement of content as a collection is copyrighted by Robert Gallagher. It is licensed under the

Creative Commons Attribution 3.0 license (http://creativecommons.org/licenses/by/3.0/).

Collection structure revised: January 10, 2012

PDF generated: June 20, 2012

For copyright and attribution information for the modules contained in this collection, see p. 597.

❚❛❜❧❡ ♦❢ ❈♦♥t❡♥ts

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Author Acknowledgements

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Student Welcome Letter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1 Sampling and Data

1.1 Sampling and Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.2 Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.3 Probability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.4 Key Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.5 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.6 Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.7 Answers and Rounding Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.8 Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

1.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

1.10 Practice: Sampling and Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

1.11 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

1.12 Lab 1: Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

1.13 Lab 2: Sampling Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

2 Descriptive Statistics

2.1 Descriptive Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

2.2 Displaying Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

2.3 Stem and Leaf Graphs (Stemplots), Line Graphs and Bar Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

2.4 Histograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

2.5 Measures of the Location of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

2.6 Measures of the Center of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

2.7 Skewness and the Mean, Median, and Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

2.8 Measures of the Spread of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

2.9 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

2.10 Practice 1: Center of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

2.11 Practice 2: Spread of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

2.12 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

2.13 Lab: Descriptive Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

3 Linear Regression and Correlation

3.1 Linear Regression and Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 103

3.2 Linear Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

3.3 Slope and Y-Intercept of a Linear Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

3.4 Scatter Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

3.5 The Regression Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

3.6 Correlation Coefficient and Coefficient of Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

3.7 Testing the Significance of the Correlation Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

3.8 Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

3.9 Outliers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

3.10 95% Critical Values of the Sample Correlation Coefficient Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

3.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

iv

3.12 Practice: Linear Regression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

3.13 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

3.14 Lab 1: Regression (Distance from School) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

3.15 Lab 2: Regression (Textbook Cost) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

3.16 Lab 3: Regression (Fuel Efficiency) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

4 Probability Topics

4.1 Probability Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

4.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

4.3 Independent and Mutually Exclusive Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

4.4 Two Basic Rules of Probability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 169

4.5 Contingency Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

4.6 Venn Diagrams (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

4.7 Tree Diagrams (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

4.8 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

4.9 Practice 1: Contingency Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

4.10 Practice 2: Calculating Probabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

4.11 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

4.12 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

4.13 Lab: Probability Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

5 Discrete Random Variables

5.1 Discrete Random Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

5.2 Probability Distribution Function (PDF) for a Discrete Random Variable . . . . . . . . . . . . . . . . . . . . 210

5.3 Mean or Expected Value and Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

5.4 Common Discrete Probability Distribution Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

5.5 Binomial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

5.6 Summary of Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

5.7 Practice 1: Discrete Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

5.8 Practice 2: Binomial Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

5.9 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

5.10 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

5.11 Lab 1: Discrete Distribution (Playing Card Experiment) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

5.12 Lab 2: Discrete Distribution (Lucky Dice Experiment) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

6 The Normal Distribution

6.1 The Normal Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

6.2 The Standard Normal Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

6.3 Z-scores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

6.4 Areas to the Left and Right of x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 255

6.5 Calculations of Probabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

6.6 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

6.7 Practice: The Normal Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260

6.8 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

6.9 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

6.10 Lab 1: Normal Distribution (Lap Times) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270

6.11 Lab 2: Normal Distribution (Pinkie Length) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

7 The Central Limit Theorem

7.1 The Central Limit Theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 279

v

7.2 The Central Limit Theorem for Sample Means (Averages) . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 280

7.3 The Central Limit Theorem for Sums . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

7.4 Using the Central Limit Theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284

7.5 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

7.6 Practice: The Central Limit Theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

7.7 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

7.8 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303

7.9 Lab 1: Central Limit Theorem (Pocket Change) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

7.10 Lab 2: Central Limit Theorem (Cookie Recipes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314

8 Confidence Intervals

8.1 Confidence Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

8.2 Confidence Interval, Single Population Mean, Population Standard Deviation

Known, Normal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319

8.3 Confidence Interval, Single Population Mean, Standard Deviation Unknown,

Student-T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 326

8.4 Confidence Interval for a Population Proportion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329

8.5 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334

8.6 Practice 1: Confidence Intervals for Averages, Known Population Standard Devi-

ation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

8.7 Practice 2: Confidence Intervals for Averages, Unknown Population Standard De-

viation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 337

8.8 Practice 3: Confidence Intervals for Proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

8.9 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

8.10 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351

8.11 Lab 1: Confidence Interval (Home Costs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354

8.12 Lab 2: Confidence Interval (Place of Birth) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357

8.13 Lab 3: Confidence Interval (Womens’ Heights) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361

9 Hypothesis Testing: Single Mean and Single Proportion

9.1 Hypothesis Testing: Single Mean and Single Proportion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367

9.2 Null and Alternate Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 368

9.3 Outcomes and the Type I and Type II Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369

9.4 Distribution Needed for Hypothesis Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370

9.5 Assumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

9.6 Rare Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371

9.7 Using the Sample to Support One of the Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372

9.8 Decision and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

9.9 Additional Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

9.10 Summary of the Hypothesis Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

9.11 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

9.12 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386

9.13 Practice 1: Single Mean, Known Population Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . . . . 387

9.14 Practice 2: Single Mean, Unknown Population Standard Deviation . . . . . . . . . . . . . . . . . . . . . . . . 389

9.15 Practice 3: Single Proportion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

9.16 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393

9.17 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 406

9.18 Lab: Hypothesis Testing of a Single Mean and Single Proportion . . . . . . . . . . . . . . .. . . . . . . . . . . . 409

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413

10 Hypothesis Testing: Two Means, Paired Data, Two Proportions

vi

10.1 Hypothesis Testing: Two Population Means and Two Population Proportions . . . . . . . . . . . . . . 419

10.2 Comparing Two Independent Population Means with Unknown Population

Standard Deviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420

10.3 Comparing Two Independent Population Means with Known Population Stan-

dard Deviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

10.4 Comparing Two Independent Population Proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

10.5 Matched or Paired Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427

10.6 Summary of Types of Hypothesis Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432

10.7 Practice 1: Hypothesis Testing for Two Proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

10.8 Practice 2: Hypothesis Testing for Two Averages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435

10.9 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437

10.10 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449

10.11 Lab: Hypothesis Testing for Two Means and Two Proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 456

11 The Chi-Square Distribution

11.1 The Chi-Square Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

11.2 Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

11.3 Facts About the Chi-Square Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462

11.4 Goodness-of-Fit Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464

11.5 Test of Independence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 471

11.6 Summary of Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476

11.7 Practice 1: Goodness-of-Fit Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477

11.8 Practice 2: Contingency Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 479

11.9 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481

11.10 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489

11.11 Lab 1: Chi-Square Goodness-of-Fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493

11.12 Lab 2: Chi-Square Test for Independence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500

12 F Distribution and ANOVA

12.1 F Distribution and ANOVA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505

12.2 ANOVA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 506

12.3 The F Distribution and the F Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 506

12.4 Facts About the F Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508

12.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 513

12.6 Practice: ANOVA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

12.7 Homework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 516

12.8 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 518

12.9 Lab: ANOVA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 524

13 Appendix

13.1 Practice Final Exam 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527

13.2 Practice Final Exam 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 536

13.3 Data Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 545

13.4 Group Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

13.5 Solution Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 559

13.6 English Phrases Written Mathematically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 563

13.7 Symbols and their Meanings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 564

13.8 Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

13.9 Notes for the TI-83, 83+, 84 Calculator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571

Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581

vii

14 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .586

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 593

Attributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597

viii

Preface1

Welcome to Collaborative Statistics, presented by Connexions. The initial section below introduces you to

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About Connexions

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Read the book online, print the PDF, or buy a copy of the book.

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About “Collaborative Statistics”

Collaborative Statistics was written by Barbara Illowsky and Susan Dean, faculty members at De Anza Col-

lege in Cupertino, California. The textbook was developed over several years and has been used in regular

and honors-level classroom settings and in distance learning classes. Courses using this textbook have been

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An on-line course based on the textbook was also developed by Illowsky and Dean. It has won an award

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3

This book is intended for introductory statistics courses being taken by students at two– and four–year

colleges who are majoring in fields other than math or engineering. Intermediate algebra is the only pre-

requisite. The book focuses on applications of statistical knowledge rather than the theory behind it. The

text is named Collaborative Statistics because students learn best by doing. In fact, they learn best by

working in small groups. The old saying “two heads are better than one” truly applies here.

Our emphasis in this text is on four main concepts:

• thinking statistically

• incorporating technology

• working collaboratively

• writing thoughtfully

These concepts are integral to our course. Students learn the best by actively participating, not by just

watching and listening. Teaching should be highly interactive. Students need to be thoroughly engaged

in the learning process in order to make sense of statistical concepts. Collaborative Statistics provides

techniques for students to write across the curriculum, to collaborate with their peers, to think statistically,

and to incorporate technology.

This book takes students step by step. The text is interactive. Therefore, students can immediately apply

what they read. Once students have completed the process of problem solving, they can tackle interesting

and challenging problems relevant to today’s world. The problems require the students to apply their

newly found skills. In addition, technology (TI-83 graphing calculators are highlighted) is incorporated

throughout the text and the problems, as well as in the special group activities and projects. The book also

contains labs that use real data and practices that lead students step by step through the problem solving

process.

At De Anza, along with hundreds of other colleges across the country, the college audience involves a

large number of ESL students as well as students from many disciplines. The ESL students, as well as

the non-ESL students, have been especially appreciative of this text. They find it extremely readable and

understandable. Collaborative Statistics has been used in classes that range from 20 to 120 students, and in

regular, honor, and distance learning classes.

Susan Dean

Barbara Illowsky

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Additional Resources13

Additional Resources Currently Available

• Glossary (Glossary, p. 5)

• View or Download This Textbook Online (View or Download This Textbook Online, p. 5)

• Collaborative Statistics Teacher’s Guide (Collaborative Statistics Teacher’s Guide, p. 5)

• Supplemental Materials (Supplemental Materials, p. 5)

• Video Lectures (Video Lectures, p. 6)

• Version History (Version History, p. 6)

• Textbook Adoption and Usage (Textbook Adoption and Usage, p. 6)

• Additional Technologies and Notes (Additional Technologies, p. 6)

• Accessibility and Section 508 Compliance (Accessibility and Section 508 Compliance, p. 6)

The following section describes some additional resources for learners and educators. These modules and

collections are all available on the Connexions website (http://cnx.org/14 ) and can be viewed online,

downloaded, printed, or ordered as appropriate.

Glossary

This module contains the entire glossary for the Collaborative Statistics textbook collection (col10522) since

its initial release on 15 July 2008. The glossary is located at http://cnx.org/content/m16129/latest/15.

View or Download This Textbook Online

The complete contents of this book are available at no cost on the Connexions website at

http://cnx.org/content/col10522/latest/16. Anybody can view this content free of charge either as an

online e-book or a downloadable PDF file. A low-cost printed version of this textbook is also available

here17 .

Collaborative Statistics Teacher’s Guide

A complementary Teacher’s Guide for Collaborative statistics is available through Connexions at

http://cnx.org/content/col10547/latest/18. The Teacher’s Guide includes suggestions for presenting con-

cepts found throughout the book as well as recommended homework assignments. A low-cost printed

version of this textbook is also available here19 .

Supplemental Materials

This companion to Collaborative Statistics provides a number of additional resources for use by students

and instructors based on the award winning Elementary Statistics Sofia online course20 , also by textbook

13This content is available online at <http://cnx.org/content/m18746/1.6/>.

14http://cnx.org/

15"Collaborative Statistics: Glossary" <http://cnx.org/content/m16129/latest/>

16Collaborative Statistics <http://cnx.org/content/col10522/latest/>

17http://my.qoop.com/store/7064943342106149/7781159220340

18Collaborative Statistics Teacher’s Guide <http://cnx.org/content/col10547/latest/>

19http://my.qoop.com/store/7064943342106149/8791310589747

20http://sofia.fhda.edu/gallery/statistics/index.html

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authors Barbara Illowsky and Susan Dean. This content is designed to complement the textbook by provid-

ing video tutorials, course management materials, and sample problem sets. The Supplemental Materials

collection can be found at http://cnx.org/content/col10586/latest/21.

Video Lectures

• Video Lecture 1: Sampling and Data22

• Video Lecture 2: Descriptive Statistics23

• Video Lecture 3: Probability Topics24

• Video Lecture 4: Discrete Distributions25

• Video Lecture 5: Continuous Random Variables26

• Video Lecture 6: The Normal Distribution27

• Video Lecture 7: The Central Limit Theorem28

• Video Lecture 8: Confidence Intervals29

• Video Lecture 9: Hypothesis Testing with a Single Mean30

• Video Lecture 10: Hypothesis Testing with Two Means31

• Video Lecture 11: The Chi-Square Distribution32

• Video Lecture 12: Linear Regression and Correlation33

Version History

This module contains a listing of changes, updates, and corrections made to the Collaborative Statistics

textbook collection (col10522) since its initial release on 15 July 2008. The Version History is located at

http://cnx.org/content/m17360/latest/34.

Textbook Adoption and Usage

This module is designed to track the various derivations of the Collaborative Statistics textbook and its

various companion resources, as well as keep track of educators who have adopted various versions for

their courses. New adopters are encouraged to provide their contact information and describe how they

will use this book for their courses. The goal is to provide a list that will allow educators using this book

to collaborate, share ideas, and make suggestions for future development of this text. The Adoption and

Usage module is located at http://cnx.org/content/m18261/latest/35.

Additional Technologies

In order to provide the most flexible learning resources possible, we invite collaboration from all instructors

wishing to create customized versions of this content for use with other technologies. For instance, you may

be interested in creating a set of instructions similar to this collection’s calculator notes. If you would like to

contribute to this collection, please use the contact the authors with any ideas or materials you have created.

Accessibility and Section 508 Compliance

21Collaborative Statistics: Supplemental Course Materials <http://cnx.org/content/col10586/latest/>

22"Elementary Statistics: Video Lecture - Sampling and Data" <http://cnx.org/content/m17561/latest/>

23"Elementary Statistics: Video Lecture - Descriptive Statistics" <http://cnx.org/content/m17562/latest/>

24"Elementary Statistics: Video Lecture - Probability Topics" <http://cnx.org/content/m17563/latest/>

25"Elementary Statistics: Video Lecture - Discrete Distributions" <http://cnx.org/content/m17565/latest/>

26"Elementary Statistics: Video Lecture - Continuous Random Variables" <http://cnx.org/content/m17566/latest/>

27"Elementary Statistics: Video Lecture - The Normal Distribution" <http://cnx.org/content/m17567/latest/>

28"Elementary Statistics: Video Lecture - The Central Limit Theorem" <http://cnx.org/content/m17568/latest/>

29"Elementary Statistics: Video Lecture - Confidence Intervals" <http://cnx.org/content/m17569/latest/>

30"Elementary Statistics: Video Lecture - Hypothesis Testing with a Single Mean" <http://cnx.org/content/m17570/latest/>

31"Elementary Statistics: Video Lecture - Hypothesis Testing with Two Means" <http://cnx.org/content/m17577/latest/>

32"Elementary Statistics: Video Lecture - The Chi-Square Distribution" <http://cnx.org/content/m17571/latest/>

33"Elementary Statistics: Video Lecture - Linear Regression and Correlation" <http://cnx.org/content/m17572/latest/>

34"Collaborative Statistics: Change History" <http://cnx.org/content/m17360/latest/>

35"Collaborative Statistics: Adoption and Usage" <http://cnx.org/content/m18261/latest/>

7

• For

information

on

general

Connexions

accessibility

features,

please

visit

http://cnx.org/content/m17212/latest/36.

• For information on accessibility features specific to the Collaborative Statistics textbook, please visit

http://cnx.org/content/m17211/latest/37.

36"Accessibility Features of Connexions" <http://cnx.org/content/m17212/latest/>

37"Collaborative Statistics: Accessibility" <http://cnx.org/content/m17211/latest/>

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Author Acknowledgements 38

For this second edition, we appreciate the tremendous feedback from De Anza College colleagues and

students, as well as from the dozens of faculty around the world who taught out of the first and preliminary

editions. We have updated Collaborative Statistics with contributions from many faculty and students. We

especially thank Roberta Bloom, who wrote new problems and additional text.

So many students and colleagues have contributed to the text, both the hard copy and open version. We

thank the following people for their contributions to the first and/or second editions.

At De Anza College:

Dr. Inna Grushko (deceased), who wrote the glossary; Diane Mathios, who checked every homework

problem in the first edition; Kathy Plum, Lenore Desilets, Charles Klein, Janice Hector, Frank Snow, Dr.

Lisa Markus, Dr. Vladimir Logvinenko (deceased), Mo Geraghty, Rupinder Sekhon, Javier Rueda, Carol

Olmstead; Also, Dr. Jim Lucas and Valerie Hauber of De Anza’s Office of Institutional Research, Mary Jo

Kane of Health Services; and the thousands of students who have used this text. Many of the students gave

us permission to include their outstanding word problems as homework.

Additional thanks:

Dr. Larry Green of Lake Tahoe Community College, Terrie Teegarden of San Diego Mesa College, Ann

Flanigan of Kapiolani Community College, Birgit Aquilonius of West Valley College.

The conversion from a for-profit hard copy text to a free open textbook is the result of many individuals and

organizations. We particularly thank Dr. Martha Kanter, Hal Plotkin, Dr. Judy Baker, Dr. Robert Maxfield

of Maxfield Foundation, Hewlett Foundation, and Connexions.

Finally, we owe much to Frank, Jeffrey, and Jessica Dean and to Dan, Rachel, Matthew, and Rebecca Il-

lowsky, who encouraged us to continue with our work and who had to hear more than their share of “I’m

sorry, I can’t” and “Just a minute, I’m working.”

38This content is available online at <http://cnx.org/content/m16308/1.10/>.

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Student Welcome Letter39

Dear Student:

Have you heard others say, “You’re taking statistics? That’s the hardest course I ever took!” They say that,

because they probably spent the entire course confused and struggling. They were probably lectured to

and never had the chance to experience the subject. You will not have that problem. Let’s find out why.

There is a Chinese Proverb that describes our feelings about the field of statistics:

I HEAR, AND I FORGET

I SEE, AND I REMEMBER

I DO, AND I UNDERSTAND

Statistics is a “do” field. In order to learn it, you must “do” it. We have structured this book so that you will

have hands-on experiences. They will enable you to truly understand the concepts instead of merely going

through the requirements for the course.

What makes this book different from other texts? First, we have eliminated the drudgery of tedious cal-

culations. You might be using computers or graphing calculators so that you do not need to struggle with

algebraic manipulations. Second, this course is taught as a collaborative activity. With others in your class,

you will work toward the common goal of learning this material.

Here are some hints for success in your class:

• Work hard and work every night.

• Form a study group and learn together.

• Don’t get discouraged - you can do it!

• As you solve problems, ask yourself, “Does this answer make sense?”

• Many statistics words have the same meaning as in everyday English.

• Go to your teacher for help as soon as you need it.

• Don’t get behind.

• Read the newspaper and ask yourself, “Does this article make sense?”

• Draw pictures - they truly help!

Good luck and don’t give up!

Sincerely,

Susan Dean and Barbara Illowsky

39This content is available online at <http://cnx.org/content/m16305/1.5/>.

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De Anza College

21250 Stevens Creek Blvd.

Cupertino, California 95014