# Probability and Statistics

### Intro

This unit is about statistics and probability. Although the two are often confused, they are different areas of mathematics. Covering them both here in one unit probably isn't helping. Ah well, it will keep you on your toes.

**Statistics** is about data (observations). In statistics we organize and analyze data. We come up with statements that somehow summarize what the data looks like all together, such as "the average on the test was 81." That statement doesn't reveal anything about anyone's individual test scores, but it still tells something about how the class did as a whole. The kid who got a 47 can run home to mom and dad and brag that his class averaged an 81, and they might be so proud they take him out for ice cream. His parents are apparently not statistics experts.

Here's another definition of statistics by people who do it for a living. Statistics is where we find the words "average,'' "mean," "median," and "mode.'' They can also be found in a dictionary, but they're slightly trickier to track down. Someone really should arrange all those words into alphabetical order.

**Probability** is about planning experiments and comparing the number of possible outcomes to the number of outcomes you want. If we roll a die and want to roll either a 1 or a 6, there are 6 possible outcomes (any of the 6 faces of the die could land facing up), but only 2 that we actually want to happen (either the 1 or the 6 facing up). Of course, if you have money on it your odds decrease substantially, as you will then have some anti-gambling karma working against you.

Probability is where we find the words "likelihood'' and "chance.'' Probability is also useful for figuring out the strength of your poker hand. Although if you are still using that card that shows what beats what, you may not be ready for probability just yet.