As a data analyst, you will occasionally need to know how your software package is calculating the statistics.
SPSS makes the algorithms for many of its tests available at:
Don’t expect them to be user-friendly if you’re not a statistician–these are the actual equations SPSS is using. But some have more detailed explanations than others, and sometimes you just need to make sure that the equation that SPSS is using is indeed the same one that your nicely detailed text is so nicely describing. This can be really useful when there are different versions of a test.