Dedication Acknowledgments About the Authors 1. Introduction and How to Use This Book Introduction The Organization of This Book How to Use This Book Key Points from the Chapter Chapter Review Questions References 2. Quantifying User Research What is User Research? Data from User Research Usability Testing A/B Testing Survey Data Requirements Gathering Key Points from the Chapter References 3. How Precise Are Our Estimates? Confidence Intervals Introduction Confidence Interval for a Completion Rate Confidence Interval for Rating Scales and Other Continuous Data Key Points from the Chapter Chapter Review Questions References 4. Did We Meet or Exceed Our Goal? Introduction One-Tailed and Two-Tailed Tests Comparing a Completion Rate to a Benchmark Comparing a Satisfaction Score to a Benchmark Comparing a Task Time to a Benchmark Key Points from the Chapter Chapter Review Questions References 5. Is There a Statistical Difference between Designs? Introduction Comparing Two Means (Rating Scales and Task Times) Comparing Completion Rates, Conversion Rates, and A/B Testing Key Points from the Chapter Chapter Review Questions References 6. What Sample Sizes Do We Need? Introduction Estimating Values Comparing Values What can I Do to Control Variability? Sample Size Estimation for Binomial Confidence Intervals Sample Size Estimation for Chi-Square Tests (Independent Proportions) Sample Size Estimation for McNemar Exact Tests (Matched Proportions) Key Points from the Chapter Chapter Review Questions References 7. What Sample Sizes Do We Need? Introduction Using a Probabilistic Model of Problem Discovery to Estimate Sample Sizes for Formative User Research Assumptions of the Binomial Probability Model Additional Applications of the Model What affects the Value of p? What Is a Reasonable Problem Discovery Goal? Reconciling the “Magic Number 5¿ with “Eight Is Not Enough¿ More about the Binomial Probability Formula and Its Small Sample Adjustment Other Statistical Models for Problem Discovery Key Points from the Chapter Chapter Review Questions References 8. Standardized Usability Questionnaires Introduction Poststudy Questionnaires Post-task Questionnaires Questionnaires for Assessing Perceived Usability of Websites Other Questionnaires of Interest Key Points from the Chapter Chapter Review Questions References 9. Six Enduring Controversies in Measurement and Statistics Introduction Is It Okay to Average Data from Multipoint Scales? Do You Need to Test at Least 30 Users? Should You Always Conduct a Two-Tailed Test? Can You Reject the Null Hypothesis When p > 0.05? Can You Combine Usability Metrics into Single Scores? What If You Need to Run More Than One Test? Key Points from the Chapter Chapter Review Questions References 10. Wrapping Up Introduction Getting More Information Good Luck! Key Points from the Chapter References APPENDIX. A Crash Course in Fundamental Statistical Concepts Introduction Types Of Data Populations and Samples Measuring Central Tendency Standard Deviation and Variance The Normal Distribution Area Under the Normal Curve Applying the Normal Curve to User Research Data Central Limit Theorem Standard Error of the Mean Margin of Error t-Distribution Significance Testing and p-Values The Logic of Hypothesis Testing Errors in Statistics Key Points from the Appendix Index