We have discussed point estimation of a parameter θ, where the inference is a guess of a single value as the value of θ. Now we will discuss interval estimation, and more generally, set estimation. The inference in a set estimation problem is the statement that θ in C, where C ⊂ Θ and C = C(x) is a set determined by the value of the data X = x observed. If θ is real-valued, then we usually prefer the set estimate C to be an interval. Therefore, interval estimators will be our main topic of discussion.