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4. The data below represent Y, sales in thousands of dollars; X1, price in cents

ID: 3236683 • Letter: 4

Question

4.   The data below represent Y, sales in thousands of dollars; X1, price in cents; X2, promotion in dollars.

Sales    Price    Promotion

53          674       3250

59          628        3589

61          536        4266

63          521        4875

65          528        4912

71          506        5763

76        453    6173    

83          399        6369

a) Give the equation of the regression line. Round to 3 decimal places.

b) Give the value of the slope for price

c) Interpret its meaning in the context of this problem. Move ethe decimal appropriately

d) Give the value of the slope for promotion.

e) Interpret its meaning in the context of this problem. Move the decimal appropriately.

f) Predict sales for price of $4.50 and $6000 spent on promotion. Move the decimal appropriately.

g) Give the calculated F for testing if the relationship is significant between sales & price and promition.

h) What is its p-value?

i) Is the relationship significant? Please answer yes or no.

j) Give the coefficient of determination.

k) Interpret its meaning in the context of this problem.

l) Give the coefficient of partial determination for price. Show your calculations.

m) Interpret its meaning in the context of this problem.

n) Give the coefficient of partial determination for promotion. Show your calculations.

o) Interpret its meaning in the context of this problem.

Explanation / Answer

(a) y = 57.790 - 0.035x1 + 0.006x2

(b) Slope = -0.035

(c) The sales decrease by $35 per 1 cent increase in the price

(d) Slope = 0.006

Regression Analysis R² 0.932 Adjusted R² 0.904 n   8 R   0.965 k   2 Std. Error   3.017 Dep. Var. y ANOVA table Source SS   df   MS F p-value Regression 620.3643 2   310.1821 34.08 .0012 Residual 45.5107 5   9.1021 Total 665.8750 7   Regression output confidence interval variables coefficients std. error    t (df=5) p-value 95% lower 95% upper std. coeff. Intercept 57.7900 0.000 x1 -0.0351 0.0443 -0.792 .4644 -0.1490 0.0788 -0.316 x2 0.0056 0.0034 1.648 .1602 -0.0031 0.0142 0.658
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