Power analyses and sample size calculations are important parts of many research projects. Often, before data are even collected, it is necessary to calculate and justify the required sample size for ...

Background: In this article, we discuss the purpose of sample size calculation in clinical trials, the need for it, and the methods by which it is accomplished. Study samples that are either too small ...

Several authors have addressed the problem of calculating sample size for a matched case-control study with a dichotomous exposure. The approach of Parker and Bregman (1986, Biometrics 42, 919-926) is ...

Wondering how many people in the United States have a smartphone? If you poll 20 people on the street, your survey won’t be representative of the entire American population. But if you just want to ...