PROBLEM 9E

Students in a semester-long health-fitness program have their percentage of body fat measured at the beginning of the semester and at the end of the semester. The following measurements give these percentages for 10 men and for 10 women:

(a) Find a 90% confidence interval for the mean of the difference in the percentages for the males.

(b) Find a 90% confidence interval for the mean of the difference in the percentages for the females.

(c) On the basis of these data, have these percentages decreased?

(d) If possible, check whether each set of differences comes from a normal distribution.

Histogram Divide data o Equal width o No overlapping Bar chart o Skew pulls direction of mean o Symmetric Numeric Summary Center, spread, and location Greek letters for population Roman letters for statistics 1. Mean µ= population mean x bar= sanple mean o ∑ Xi all over n= sample mean k=0 2. Mean vs. Median a. Mean used the most b. N is small when outliers occur c. Use median, mean is too affected Spread 1. Range (MaxMin) a. Sensitive to outliers 2. IQR a. Not sensitive to outliers Variability XiX bar