What stratification variable(s) would you use for each of the following situations:

a A political poll to estimate the percentage of registered voters in Arizona that approve of the governor’s performance.

b An e-mail survey of students at your university, to estimate the total amount of money students spend on textbooks in a term.

c A sample of high schools in New York City to estimate what percentage of high schools offer one or more classes in computer programming.

d A sample of public libraries in California to study the availability of computer resources, and the per capita expenditures.

e A survey of anglers visiting a freshwater lake, to learn about which species of fish are preferred.

f An aerial survey to estimate the number of walrus in the pack ice near Alaska between 173° East and 154° West longitude.

g A sample of prime-time (7–10 pm, Monday through Saturday; 6–10 pm, Sunday) TV programs on CBS to estimate the average number of promotional announcements (ads for other programming on the station) per hour of broadcast.