One of the most widely used programs for statistical analysis in the social sciences. It is a proprietary program and very expensive (~$1500 with a few of the advanced modules). If you are doing this sort of stuff on you own, learning "R" will save you a bundle. If you feel compelled to use SPSS (perhaps your boss or client is comitted or should be) and you have to pay for it yourself try a search for "SPSS Graduate" on Ebay, AbeBooks and Amazon. It's quite rare but I have succeeded twice in finding a copy for less that $25. Older versions (9 through 13) are preferable.