CS 70 Discrete Mathematics and Probability Theory

Spring 2015 Vazirani Note 23

How to Lie with Statistics

There are three kinds of lies: lies, damned lies, and statistics, as Mark Twain is reputed to have said. In

this lecture we will see why statistics are so easy to misuse, and some of the ways we must be careful while

evaluating statistical claims.

First a very simple but important point about statistics. Statistics cannot be used to establish causation,

they can only show correlations. As an example, the governor of a certain state is concerned about the test

scores of high school students in the state. One of his aides brings up an interesting statistic: there is a very

strong...