Write the null and alternative hypotheses you would use to test each situation.
a) In the 1950s, only about 40% of high school graduates went on to college. Has the percentage changed?
b) Twenty percent of cars of a certain model have needed costly transmission work after being driven between 50,000 and 100,000 miles. The manufacturer hopes that a redesign of a transmission component has solved this problem.
c) We field-test a new-flavor soft drink, planning to market it only if we are sure that over 60% of the people like the flavor.