Question 10 (1 point)

Year	Advertising	Quality_Control	Sales_Revenue
1	8	3	97.5
2	7	4	107.0
3	7	5	105.5
4	9	4	111.6
5	9	5	119.8
6	10	5	134.7
7	11	3	117.1
8	12	3	127.5
9	13	4	139.5
10	11	4	112.0
11	10	5	141.4
12	12	6	133.2
13	14	6	162.4
14	15	5	152.4
15	15	4	125.0

This is same regression data as the previous question. BUT, you now need to run a new regression using BOTH Advertising and Quality Control as independent variables. Your Excel regression output now will show observations = 15 and R² = 0.77 (approximate). When you did the regression using only Advertising, the standard error of the regression was about 12.6. This meant that any forecasted value for Sales_Revenue had a 95% confidence interval of the estimated value +/- 2*12.6 or +/- 25.2. This is a confidence interval that is 50.4 units in size. The improved fit of the model using Advertising and Quality Control is seen in the lower standard error of the regression. The standard error of the regression now = ______(approximate) which leads to a confidence interval not of 50.4 units in size but only _____ in size.

Question 10 options:

a)	11.2; 44.8

b)

7.9; 31.6

c)

9.5; 38

d)

6.7; 26.8