In each case, choose whether the appropriate test is a one-proportion z-test or a two-proportion z-test. Name the population(s).
a. A researcher takes a random sample of 4-year-olds to find out whether girls or boys are more likely to know the alphabet.
b. A pollster takes a random sample of all U.S. adult voters to see whether more than 50% approve of the performance of the current U.S. president.
c. A researcher wants to know whether a new heart medicine reduces the rate of heart attacks compared to an old medicine.
d. A pollster takes a poll in Wyoming about home schooling to find out whether the approval rate for men is equal to the approval rate for women.
e. A person is studied to see whether he or she can predict the results of coin flips better than chance alone.