Deborah Rumsey, PhD, is a Professor of Statistics and Statistics Education Specialist at The Ohio State University. She is the author of Statistics For Dummies, Statistics Workbook For Dummies, Statistics II For Dummies, and Probability For Dummies.

Introduction 1

About This Book 1

Foolish Assumptions 2

Icons Used in This Book 3

Beyond the Book 3

Where to Go from Here 4

Unit 1: Getting Started with Statistics 5

Chapter 1: The Statistics of Everyday Life 7

Statistics and the Media: More Questions than Answers? 8

Probing popcorn problems 8

Venturing into viruses 8

Comprehending crashes 9

Mulling malpractice 9

Belaboring the loss of land 10

Scrutinizing schools 10

Scanning sports 10

Banking on business news 11

Touring the travel news 12

Surveying sexual stats 12

Breaking down weather reports 13

Using Statistics at Work 13

Delivering babies - and information 13

Posing for pictures 14

Poking through pizza data 14

Statistics in the office 14

Chapter 2: Taking Control: So Many Numbers, So Little Time 15

Detecting Errors, Exaggerations, and Just Plain Lies 16

Checking the math 16

Uncovering misleading statistics 17

Looking for lies in all the right places 22

Feeling the Impact of Misleading Statistics 23

Chapter 3: Tools of the Trade 25

Thriving in a Statistical World 25

Statistics: More than Just Numbers 26

Designing Appropriate Studies 28

Surveys (Polls) 28

Experiments 29

Collecting Quality Data 30

Sample, random, or otherwise 30

Bias 32

Grabbing Some Basic Statistical Jargon 33

Data 33

Data set 34

Variable 34

Population 34

Statistic 35

Parameter 35

Mean (Average) 36

Median 36

Standard deviation 36

Percentile 37

Standard score 37

Distribution and normal distribution 38

Central Limit Theorem 38

z-values 39

Margin of error 39

Confidence interval 40

Hypothesis testing 41

p-values 42

Statistical significance 42

Correlation, regression, and two-way tables 43

Drawing Credible Conclusions 44

Reeling in overstated results 44

Questioning claims of cause and effect 44

Becoming a Sleuth, Not a Skeptic 45

Unit 2: Number-Crunching Basics 47

Chapter 4: Crunching Categorical Data 49

Summing Up Data with Descriptive Statistics 49

Crunching Categorical Data: Tables and Percents 50

Counting on the frequency 50

Relating with percentages 52

Two-way tables: Summarizing multiple measures 54

Interpreting counts and percents with caution 55

Practice Questions Answers and Explanations 57

Whaddya Know? Chapter 4 Quiz 60

Answers to Chapter 4 Quiz 62

Chapter 5: Means, Medians, and More 65

Measuring the Center with Mean and Median 65

Averaging out to the mean 66

Splitting your data down the median 68

Comparing means and medians: Histograms 70

Accounting for Variation 74

Reporting the standard deviation 75

Being out of range 78

Examining the Empirical Rule (68-95-99.7) 79

Measuring Relative Standing with Percentiles 83

Calculating percentiles 83

Interpreting percentiles 85

Gathering a five-number summary 88

Exploring interquartile range 89

Practice Questions Answers and Explanations 90

Whaddya Know? Chapter 5 Quiz 97

Answers to Chapter 5 Quiz 98

Chapter 6: Getting the Picture: Graphing Categorical Data 99

Take Another Little Piece of My Pie Chart 100

Tallying personal expenses 100

Bringing in a lotto revenue 101

Ordering takeout 102

Projecting age trends 103

Raising the Bar on Bar Graphs 108

Tracking transportation expenses 108

Making a lotto profit 110

Tipping the scales on a bar graph 110

Pondering pet peeves 111

Practice Questions Answers and Explanations 117

Whaddya Know? Chapter 6 Quiz 123

Answers to Chapter 6 Quiz 124

Chapter 7: Going by the Numbers: Graphing Numerical Data 125

Handling Histograms 126

Making a histogram 126

Interpreting a histogram 130

Putting numbers with pictures 137

Detecting misleading histograms 139

Examining Boxplots 143

Making a boxplot 143

Interpreting a boxplot 146

Tackling Time Charts 152

Interpreting time charts 152

Understanding variability: Time charts versus histograms 153

Spotting misleading time charts 153

Practice Questions Answers and Explanations 159

Whaddya Know? Chapter 7 Quiz 165

Answers to Chapter 7 Quiz 166

Unit 3: Distributions and the Central Limit Theorem 167

Chapter 8: Coming to Terms with Probability 169

A Set Notation Overview 169

Noting outcomes: Sample spaces 170

Noting subsets of sample spaces: Events 171

Noting a void in the set: Empty sets 172

Putting sets together: Unions, intersections, and complements 172

Probabilities of Events Involving A and/or B 173

Probability notation 174

Marginal probabilities 175

Union probabilities 175

Intersection ( joint) probabilities 175

Complement probabilities 176

Conditional probabilities 176

Understanding and Applying the Rules of Probability 178

The complement rule (for opposites, not for flattering a date) 178

The multiplication rule (for intersections, not for rabbits) 179

The addition rule (for unions of the nonmarital nature) 180

Recognizing Independence in Multiple Events 182

Checking independence for two events with the definition 182

Using the multiplication rule for independent events 183

Including Mutually Exclusive Events 184

Recognizing mutually exclusive events 184

Simplifying the addition rule with mutually exclusive events 185

Distinguishing Independent from Mutually Exclusive Events 186

Comparing and contrasting independence and exclusivity 186

Checking for independence or exclusivity in a 52-card deck 187

Avoiding Probability Misconceptions 189

Predictions Using Probability 190

Practice Questions Answers and Explanations 192

Whaddya Know? Chapter 8 Quiz 196

Answers to Chapter 8 Quiz 197

Chapter 9: Random Variables and the Binomial Distribution 199

Defining a Random Variable 200

Discrete versus continuous 200

Probability distributions 202

The mean and variance of a discrete random variable 202

Identifying a Binomial 203

Checking binomial conditions step by step 204

No fixed number of trials 204

More than success or failure 205

Trials are not independent 205

Probability of success (p) changes 205

Finding Binomial Probabilities Using a Formula 207

Finding Probabilities Using the Binomial Table 210

Finding probabilities for specific values of X 210

Finding probabilities for X greater-than, less-than, or between two values 211

Checking Out the Mean and Standard Deviation of the Binomial 212

Practice Questions Answers and Explanations 214

Whaddya Know? Chapter 9 Quiz 216

Answers to Chapter 9 Quiz 217

Chapter 10: The Normal Distribution 219

Exploring the Basics of the Normal Distribution 219

Meeting the Standard Normal (Z-) Distribution 223

Checking out Z 223

Standardizing from X to Z 223

Finding probabilities for Z with the Z-table 225

Finding Probabilities for a Normal Distribution 227

Knowing Where You Stand with Percentiles 230

Finding X When You Know the Percent 232

Figuring out a percentile for a normal distribution 232

Translating tricky wording in percentile problems 234

Normal Approximation to the Binomial 236

Practice Questions Answers and Explanations 239

Whaddya Know? Chapter 10 Quiz 248

Answers to Chapter 10 Quiz 249

Chapter 11: The t-Distribution 251

Basics of the t-Distribution 251

Comparing the t- and Z-distributions 251

Discovering the effect of variability on t-distributions 252

Using the t-Table 253

Finding probabilities with the t-table 253

Figuring percentiles for the t-distribution 256

Picking out t*-values for confidence intervals 257

Studying Behavior Using the t-Table 258

Practice Questions Answers and Explanations 259

Whaddya Know? Chapter 11 Quiz 260

Answers to Chapter 11 Quiz 261

Chapter 12: Sampling Distributions and the Central Limit Theorem 263

Defining a Sampling Distribution 264

The Mean of a Sampling Distribution 265

Measuring Standard Error 266

Sample size and standard error 266

Population standard deviation and standard error 267

Looking at the Shape of a Sampling Distribution 269

Case 1: The distribution of X is normal 269

Case 2: The distribution of X is not normal - Enter the Central Limit Theorem 269

Finding Probabilities for the Sample Mean 273

The Sampling Distribution of the Sample Proportion 275

Finding Probabilities for the Sample Proportion 278

Practice Questions Answers and Explanations 280

Whaddya Know? Chapter 12 Quiz 283

Answers to Chapter 12 Quiz 284

Unit 4: Guesstimating and Hypothesizing with Confidence 285

Chapter 13: Leaving Room for a Margin of Error 287

Seeing the Importance of that Plus or Minus 287

Finding the Margin of Error: A...