Chapter 10. Power analysis


This chapter covers
  • Determining sample size requirements
  • Calculating effect sizes
  • Assessing statistical power


As a statistical consultant, I am often asked the question, “How many subjects do I need for my study?” Sometimes the question is phrased this way: “I have x number of people available for this study. Is the study worth doing?” Questions like these can be answered through power analysis, an important set of techniques in experimental design.

Power analysis allows you to determine the sample size required to detect an effect of a given size with a given degree of confidence. Conversely, it allows you to determine the probability of detecting an effect of a given size with a given level of confidence, ...

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