2. Data from a sample of 5 pharmacies are used to examine the relation between prescription

sales volume and the percent of prescription ingredients purchase directly from the suppliers. The

sample data are shown here:

Sales Volume, y % of Ingredients

(in $1,000) Purchased Directly, x xy y x-square

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25

10

250

625

100

55

18

990

3,025

324

50

25

1,250

2,500

625

75

40

3,000

5,625

1,600

110

50

5,500

1,2100

2,500

Total 315

143

10,990

23,875

5,149

a) Find the Least Square Error regression line.

b) Interpret the meaning of slope.

c) Predict sales volume for a pharmacy that purchase 15% of its prescription ingredients

directly from the supplier.