Biostatistics For Dummies

Chapter 10

Having Confidence in Your Results

In This Chapter

Investigating the basics of confidence intervals

Determining confidence intervals for a number of statistics

Linking significance testing to confidence intervals

In Chapter 9, I show you how to express the precision of a numeric result using the standard error (SE) and how to calculate the SE (or have a computer calculate it for you) for the most common kinds of numerical results you get from biological studies — means, proportions, event rates, and regression coefficients. But the SE is only one way of specifying how precise your results are. In this chapter, I describe another commonly used indicator of precision — the confidence interval (CI).

I assume that you’re familiar with the concepts of populations, samples, and statistical estimation theory (see Chapter 3 if you’re not) and that you know what standard errors are (see Chapter 9 if you don’t). Always keep in mind that when you conduct any kind of research study, such as a clinical trial, you’re studying a small sample of subjects (like 50 adult volunteers with ...