Interpreting regression coefficients and explanation the Statistical Significance.
The director of marketing at vanguard corporation believe that sales of the company's bright side laundry detergent (S) are related to Vanguard's own advertising expenditure (A), as well as the combined advertising expenditures of its 3 biggest rival detergents ( R). The marketing director collects 36 weekly observations on S, A, and R to estimate the following multiple regression equation:
S = a + bA + cR
Where S, A, and R are measured in dollars per week. Vanguard's marketing director is comfortable using parameter estimates that are statistically significant at the 10% level or better.
a. What sign does the marketing director expect a, b, and c to have?
b. Interpret the coefficients a, b, and c.
The regression output from the computer is as follows:
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DEPENDENT VARIABLE:
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S
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R-SQUARE
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F-RATIO
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P-VALUE ON F
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OBSERVATIONS:
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36
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0.2247
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4.781
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0.0150
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Parameter
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Standard
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Variable
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Estimate
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Error
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T-Ratio
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P-Value
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c. Does Vanguard's advertising expenditures have a statistically significant effect on the sale of Brightside detergent? Clarify using the appropriate p-value
d. Does advertising by its three largest rivals affect sales of Bright Side detergent in a statistically way? Elucidate using the appropriate p-value.
e. What fraction of the total variation in sales of Bright Side remains unexplained? What can the marketing director do to increase the explanatory power of sales equation? What other explanatory variables may be added to this equation?
f. What is the expected level of sales each week while Vanguard spends $40,000 per week and the combined advertising expenditures for the three rivals are $100,000 per week?