Here are data from a small bookstore.

Number of SalespeopleWorking Sales (in $1000’s)

2 ............. 10

3 ............. 11

7 ............. 13

9 ............. 14

10 ............. 18

10 ............. 20

12 ............. 20

15 ............. 22

16 ............. 22

20 ............. 26

x̄ = 10.4 .......... y-bar = 17.6

SD(x) = 5.64 ........ SD(y) = 5.34

The regression line is:

Sales = 8.10 + 0.9134

Number of Salespeople Working. The assumptions and conditions for regression are met, and from technology we learn that

SE(b1) = 0.0873 se = 1.477

a) Find the predicted Sales on a day with 12 employees working.

b) Find a 95% confidence interval for the mean Sales on days that have 12 employees working.

c) Find the 95% prediction interval for Sales on a day with 12 employees working.