This is a program i made for myself, and it was so useful that i decided to share.
What the program does is calculates and displays the probability of type I and II errors for a z-test and also the power of the test.
The program will calculate either from actual data or statistics.  To use data, you can either use a pre-existing list or create one in the program (if you put it in the format {x1,x2,x3,...xn}).
The calculations may differ from the z-table due to the table's rounding error.
If you don't know what a z-test or type I and II errors are this program is not for you (yet).