Becoming a Data Head

CHAPTER 7Challenge the Statistics

Kent Brockman: Mr. Simpson, how do you respond to the charge that petty vandalism such as graffiti is down 80% while heavy sack beatings are up a shocking 900%?

Homer: Oh, people can come up with statistics to prove anything, Kent. Forty percent of all people know that.

—The Simpsons

Have you ever heard a statistical claim in the news or in the workplace that you wanted to understand, appreciate, or perhaps challenge? That's what this chapter is about. We're going to teach you about statistical inference, how to use inferential statistics, how to challenge their results, and we'll give you the questions you need to ask to fully understand the underlying inferences being made.

QUICK LESSONS ON INFERENCE

Recall from Chapter 3, “Prepare to Think Statistically,” that statistical inference enables us to sample data from the world we live in to then make informed guesses about that world.

In this section, we'll walk you through a series of short examples to show how intuitive statistical inference can be, while gradually adding in formal statistical language (some of which you learned earlier in the book, but a reminder never hurts). The good news is that, no matter your background with statistics, you'll be able to follow the logic of statistical inference we present here.

Give Yourself Some Wiggle Room

Polling data is a common and important example of inferential statistics. You can't survey everyone—you can only poll those in the sample