July 2013
Beginner
408 pages
10h 42m
English
Content preview from Biostatistics For Dummies
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Chapter 26
Ten Easy Ways to Estimate How Many Subjects You Need
In This Chapter
Quickly estimating sample size for several basic kinds of tests
Adjusting for different levels of power and alpha
Adjusting for unequal group sizes and for attrition during the study
Sample-size calculations tend to frighten researchers and send them running to the nearest statistician. But if you’re brainstorming a possible research project and you need a ballpark idea of how many subjects to enroll, you can use the ten quick and (fairly) easy rules of thumb in this chapter.
Before you begin, look at Chapter 3, especially the sections on hypothesis testing and the power of a test, so that you have the basic idea of what power and sample-size calculations are all about. Think about the effect size of importance (such as the difference in some variable between two groups, or the degree of correlation between two variables) that you want to be able to detect. Then find the rule for the statistical test that’s appropriate for the primary objective of your study.
The first six sections tell you how many ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.