It's time for us to put descriptive statistics down for the time being. It was fun for a while, but we're no longer content just determining the properties of observed data; now we want to start making deductions about data we haven't observed. This leads us to the realm of inferential statistics. In data analysis, probability is used to quantify uncertainty of our deductions about unobserved data. In the land of inferential statistics, probability reigns queen. Many regard her as a harsh mistress, but that's just a rumor.