This chapter demonstrates how to calculate power for a variety of statistical designs with PROC POWER and PROC GLMPOWER now available in SAS Version 9.1. Cohen's book is the basis for many of the calculations, though as you will see when comparing his tabled results to the outputs of these programs, the SAS statements allow much flexibility to extend his tables to your own situation.
Several sections demonstrate how PROC MIXED can be utilized as a power analysis or study planning tool. The other side of this data analysis tool opens a wide variety of statistical designs that previously were difficult or not possible to produce power calculations.
As you explore the contents of this chapter, it will be helpful to copy the examples into PC SAS and combine the results not only with PROC TABULATE, but also SAS GRAPH, particularly PROC GPLOT (read Section 1 for more details) to visually see how power changes as other aspects of the power inputs are modified.
First, you will need a broad perspective on what power analysis is about and some simple illustrations with PROC POWER and PROC GLMPOWER available in the following document.
After reading this document you will be able to better appreciate the calculations shown in the following command files.
Sample SAS programs to compute power for a variety of designs.