10.78 Females or males have more close friends? A recent GSS reported that the 486 surveyed females had a mean of 8.3 close friends 1s = 15.62 and the 354 surveyed males had a mean of 8.9 close friends 1s = 15.52.

a. Estimate the difference between the population means for males and females.

b. The 95% confidence interval for the difference between the population means is 0.6 { 2.1. Interpret.

c. For each gender, does it seem like the distribution of number of close friends is normal? Why? How does this affect the validity of the confidence interval in part b?