In Chapter 4, Probability, we mentioned that the mean height of US females is 65 inches. Now pretend we didn't know this fact—how could we find out what the average height is?
We can measure every US female, but that's untenable; we would run out of money, resources, and time before we even finished with a small city!
Inferential statistics gives us the power to answer this question using a very small sample of all US women. We can use the sample to tell us something about the population we drew it from. We can use observed data to make inferences about unobserved data. By the end of this chapter, you too will be able to go out and collect a small amount of data and use it to reason about the world!