This section demonstrates how you can use the different SAS power analysis tools mentioned in the section Overview to generate graphs, tables, and narratives; implement your own power formulas; and simulate empirical power.

Suppose you want to compute the power of a two-sample t test. You conjecture that the mean difference is between 5 and 6 and that the common group standard deviation is between 12 and 18. You plan to use a significance level between 0.05 and 0.1 and a sample size between 100 and 200. The following SAS statements use the POWER procedure to compute the power for these scenarios:

proc power;
   twosamplemeans test=diff
      meandiff = 5 6
      stddev = 12 18
      alpha = 0.05 0.1
      ntotal = 100 200
      power = .;
run;

Figure 18.1 shows the results. Depending on the plausibility of the various combinations of input parameter values, the power ranges between 0.379 and 0.970.

The following seven sections illustrate additional ways of displaying these results using the different SAS tools.