Most binomial probability calculations required in these exercises can be done by using Table C or the Normal approximation. Your instructor may request that you use the binomial probability formula or software. In exercises requiring the Normal approximation, you should use the continuity correction if you studied that topic.

Question 5.26

5.26 Paying for music downloads, continued.

Refer to Exercise 5.24. Suppose that only 60% of the U.S. teenagers used a fee-based website to download music.

  1. If you interview 15 U.S. teenagers at random, what is the mean of the count who used a fee-based website to download music? What is the mean of the proportion in your sample who used a fee-based website to download music?
  2. Repeat the calculations in part (a) for samples of size 150 and 1500. What happens to the mean count of successes as the sample size increases? What happens to the mean proportion of successes?