An article (A. Jennings, "What's Good for a Business Can Be Hard on Friends," The NewYork Times, August 4, 2007, pp. C1-C2) reported that according to a poll, the mean number of cell phone calls per month was 290 for 18- to 24-year-olds and 194 for 45- to 54-year-olds, whereas the mean number of text messages per month was 290 for 18- to 24-year-olds and 57 for 45- to 54-year-olds. Suppose that the poll was based on a sample of 100 18- to 24-year-olds and 100 45- to 54-year-olds and that the standard deviation of the number of cell phone calls per month was 100 for 18- to 24-year-olds and 90 for 45- to 54-year-olds, whereas the standard deviation of the number of text messages per month was 90 for 18- to 24-year-olds and 77 for 45- to 54- year-olds. Assume a level of significance of 0.05.
a. Is there evidence of a difference in the variances of the number of cell phone calls per month for 18- to 24-yearolds and for 45- to 54-year-olds?
b. Is there evidence of a difference in the mean number of cell phone calls per month for 18- to 24-year-olds and for 45- to 54-year-olds?
c. Construct and interpret a 95% confidence interval estimate for the difference in the mean number of cell phone calls per month for 18- to 24-year-olds and 45- to 54-year-olds.
d. Is there evidence of a difference in the variances of the number of text messages per month for 18- to 24-yearolds and 45- to 54-year-olds?
e. Is there evidence of a difference in the mean number of text messages per month for 18- to 24-year-olds and 45- to 54-year-olds?
f. Construct and interpret a 95% confidence interval estimate for the difference in the mean number of text messages per month for 18- to 24-year-olds and 45- to 54-year-olds.
g. Based on the results of (a) through (f), what conclusions can you make concerning cell phone and text message usage between 18- to 24-year-olds and 45- to 54-year-olds?