A study found that the average American buys 4.6 movie tickets per year, compared to just 1.9 for the average Spaniard. Assuming that the data values in file XR04049 represent the number of movie ticket purchases reported by 100 American respondents,
a. Select a simple random sample of 20 data values. Compute the sample mean. 

b. Select another simple random sample of 20 data values, and compute the mean.
c. To two decimal places, compare the mean of the sample in part (a) with the mean of the sample in part (b). Are the values identical? Would you expect them to be? How do they compare to the mean of the 100 data values from which the samples were drawn? (We will learn more about this topic in Chapter 8, Sampling Distributions.)