In the process of collecting weight and height data from 29 female and 81 male students at your university, you also asked the students for the number of siblings they have. Although it was not quite clear to you initially what you would use that variable for, you construct a new theory that suggests that children who have more siblings come from poorer families and will have to share the food on the table. Although a friend tells you that this theory does not pass the “straight-face” test, you decide to hypothesize that peers with many siblings will weigh less, on average, for a given height. In addition, you believe that the muscle/fat tissue composition of male bodies suggests that females will weigh less, on average, for a given height. To test these theories, you perform the following regression:

Studentw = –229.92 – 6.52 Female + 0.51 Sibs+ 5.58 Height,

R2=0.50, SER = 21.08

where Studentw is in pounds, Height is in inches, Female takes a value of 1 for females and is 0 otherwise, Sibs is the number of siblings.

a. Interpret the regression results.

b. Build the 95% confidence interval for female coefficient if the standard deviation is 1.25, build the 95% confidence interval for female coefficient if the standard deviation is 2.5. How different are they? How does this difference impact your analysis?