This simulation illustrates the effect of (a) sample size, (b) the difference between population mean and hypothesized mean, (c) the standard deviation, (d) the type of test (one-tailed or two), and (e) significance level on the power of a two-sample t test.

You specify the difference between the population mean and hypothesized mean by either enterng text in the box or by moving the slider. The populaton standard deviation can be entered in the box or specified by the pop-up menu. Finally, you specify the number of tails of the test. A power graph for the significance level 0.10, 0.05, and 0.01 significance levels as a funtion of sample size is displayed.