With this chapter, we begin formal inference. From here on, we will want to say something about an unknown population parameter based solely on a sample.

There are two sorts of questions we can address. First, we can ask, “based on this sample, what is our best estimate for some population parameter; and how good is this estimate?” Second, we can ask, “based on this sample, can we conclude that something is true of a population parameter; and how sure are we?”