A manufacturer of electronic components for the computer industry is investigating the relationship between sales (Y) an

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A manufacturer of electronic components for the computerindustry is investigating the relationship between sales (Y) andnumber of sales people (X1), price of product(X2), and price of competitor’s product (X3).Based on the following data for eighteen periods and associatedregression analysis, answer the following questions.
Sales ($1,000s)
Number of Sales People
Price of Product
($)
Price of Competitor’s
Product ($)
Y
X1
X2
X3
50
5
30
25
120
7
30
26
140
11
33
28
135
16
34
30
163
16
33
31
233
16
36
34
241
21
40
37
255
27
45
42
286
26
50
48
330
30
53
54
389
33
58
58
425
36
60
61
445
38
71
72
472
37
80
81
501
37
90
93
510
38
92
92
490
36
92
90
505
37
94
94
(a) Which model would you recommend if the decision-maker wantsto select a single independent variable model? and why?
(b) Is it useful to include X3 in the model whenX1 is already in the model? Explain
(c) What is the model corresponding to the regression Y vs.X1, X3? Use the p-value in this model to testits usefulness.
(d) Of all the regressions considered, which would you suggestas the best model? and why?
(e) For the model Y vs. X1,X3, comment about the normality assumption and theresidual plots.
(f) Develop and interpret a 95% prediction confidenceinterval for the sales when the company employs 15 sales people andthe competitor’s product price is $28.