Suppose a church is considering purchasing new hymnals (books that contain the hymns sung during the service) and wants to sample the congregation to see whether its members sup port the purchase. They might ask those in the sample to choose a number from 1 to 5, where 1 means new hymnals should definitely not be purchased, 3 is neutral, and 5 means they should definitely be purchased. Why might you want to stratify your samples into two groups: the choir (with other musical performers) and those not in the choir?