Calculating the power when using a t-test is similar to using a normal distribution. One difference is that we use the command associated with the t-distribution rather than the normal distribution. Here we repeat the test above, but we will assume that we are working with a sample standard deviation rather than an exact standard deviation. We will explore three different ways to calculate the power of a test. The first method makes use of the scheme many books recommend if you do not have the non-central distribution available. The second does make use of the non-central distribution, and the third makes use of a single command that will do a lot of the work for us.