The last dialog box is contrasts. Contrasts are differences in mean scores. It allows you to group multiple groups into one and test the average mean of the two groups against our third group. Please note that the contrast is not always the mean of the pooled groups! Contrast = (mean first group + mean second group)/2. It is only equal to the pooled mean, if the groups are of equal size. It is also possible to specify weights for the contrasts, ., for group 1 and for group 2. We do not specify contrasts for this demonstration.
The Sample Size/Power Analysis Calculator is a tool for those struggling with a power analysis. Simply identify the statistical test to be conducted and the calculator will calculate your sample size for a power of .80 of an alpha of .05 for small, medium and large effect sizes. The sample size/power analysis calculator then presents the calculation in a write-up with references. This write-up can easily be integrated in your dissertation or theses document. This write-up also includes qualitative sample size calculation and write-up too!