The following regression model was estimated to explain the annual sales from a direct marketing campaign:

where
St = $ sales in year t
Pt = $ promotional expenditure in year t
Mt = $ product mailing expenditures in year t
Ct = Number of pamphlets distributed in year t
The estimated standard errors are given (in parentheses) corresponding to the coefficient estimates. The marketing director suggests that we should increase our mailing expenditures next year by sending more shipments first class, rather than via parcel post, since the mailing expenditure coefficient is "significant" in the regression. What would you advise?

Transcribed Image Text:

S,-551.5P 6.0M,0.25C, R2 0.92 (2.1) (0.5) (0.55