In: Statistics and Probability
1. Here are the data from a small bookstore:
|
Number of Salespeople Working |
Sales (in $1000s) |
|
2 |
10 |
|
3 |
11 |
|
7 |
13 |
|
9 |
14 |
|
10 |
18 |
|
10 |
20 |
|
12 |
20 |
|
15 |
22 |
|
16 |
22 |
|
20 |
26 |
a. Compute the correlation coefficient between number of salespeople and sales. Interpret the correlation coefficient. 6
b. Assuming the conditions for regression are met, find the estimated least-squares regression line and predicted sales on a day with 12 employees working. 7
c. If you expect the population regression coefficient to be positive, perform the hypothesis test of the regression coefficient at significance level of 0.05. 8
d. Find 95% prediction interval for Sales on a day with 12 employees working. 7
e. Comment on the overall quality of the fitted model using appropriate index. 7
a. Compute the correlation coefficient between number of salespeople and sales. Interpret the correlation coefficient
Sol:







the correlation coefficient between number of salespeople and sales is 0.9653.
b. Assuming the conditions for regression are met, find the estimated least-squares regression line and predicted sales on a day with 12 employees working
Sol:

The regression equaion is Y=8.1005+0.9134X
The predicted sales on a day with number of sales people
working
Y=8.10+0.913(12)
=18.9