Sample size calculation is often needed in the research plan of a grant proposal or a research study protocol. Here is a few tips on how to calculate the statistical power and sample size using various widely-used statistical methods.

**Exploratory Factor Analysis**

In their book, Comrey and Lee (1992) give a few rules of thumb on the sample size requirements for Exploratory Factor Analysis. These suggestions are cited by Tabachnick and Fidell (1996, p. 640). Tabachnick and Fidell (1996) suggest that "As a general rule of thumb, it is comforting to have at least 300 cases for factor analysis". Here is what is in Tabachnick and Fidell (1996):

- very poor: N ~ 50
- poor: N ~ 100
- fair: N ~ 200
- good: N ~ 300
- very good: N ~ 500
- excellent: N ~ 1000