A critically important aspect of customer service in a supermarket is the waiting time at the checkout (defined as the time the customer enters the line until he or she is served). Data were collected during time periods in which a constant number of checkout counters were open. The total number of customers in the store and the waiting times (in minutes) were recorded. The results are given below.
| Day |
Customers |
Time |
| 1 |
15.00 |
1.50 |
| 2 |
18.00 |
1.20 |
| 3 |
9.00 |
0.80 |
| 4 |
7.00 |
0.50 |
| 5 |
19.00 |
2.00 |
| 6 |
30.00 |
2.50 |
| 7 |
27.00 |
3.00 |
| 8 |
13.00 |
2.00 |
| 9 |
11.00 |
1.70 |
| 10 |
9.00 |
0.50 |
| 11 |
21.00 |
2.00 |
| 12 |
35.00 |
5.20 |
| 13 |
25.00 |
2.30 |
| 14 |
8.00 |
0.20 |
| 15 |
16.00 |
0.70 |
| 16 |
21.00 |
2.50 |
| 17 |
17.00 |
1.00 |
| 18 |
22.00 |
3.80 |
| 19 |
16.00 |
1.50 |
| 20 |
24.00 |
2.80 |
| 21 |
14.00 |
1.00 |
| 22 |
15.00 |
1.70 |
| 23 |
21.00 |
3.00 |
| 24 |
27.00 |
2.80 |
| 25 |
17.00 |
1.00 |
| 26 |
21.00 |
2.50 |
| 27 |
20.00 |
2.90 |
| 28 |
31.00 |
3.40 |
| 29 |
38.00 |
4.00 |
| 30 |
42.00 |
4.80 |
PLEASE SHOW ALL CALCULATIONS
a. Construct a scatter plot.
b. Assuming a linear relationship, use the least-squares method to determine the regression coefficients b0 and b1.
c. Interpret the meaning of the slope, in this problem.
d. Predict the waiting time when there are 20 customers in the store.