Multistage sampling Th e previous exercise gives part of the description of a sample survey from the Wall Street Journal.

(a) It appears that the sample was taken in several stages. Why can we say this?

(b) Th e fi rst stage no doubt used a stratifi ed sample, though the Journal does not say this. Explain why it would be bad practice to use an SRS from a large number of

“geographic points” across the country rather than a stratifi ed sample of such points.