Explain what is meant by the notion of "trimming" a multiple regression result. Use the following example to illustrate your understanding of this concept.
A bicycle manufacturer maintains records over 20 years of the following measured in appropriate units per year: unit sales (dependent variable), average retail price in dollars, co-operative advertising amount in dollars, competitors' average retail price in dollars, number of retail locations selling the bicycle manufacturer's brand, and whether or not the winner of the Tour de France was riding the manufacturers' brand (coded as a dummy variable where 0 = no, and 1-yes).
The initial multiple regression result determines the following:
Variable Significance Level
Average retail price in dollars .................. .001
Cooperative advertising amount in dollars ..... .202
Competitors' average retail price in dollars ..... .028
Number of retail locations ........................ .591
Tour de France ......................................... .032
Using the "enter" method, what would be the trimming steps you would expect to undertake to identify the significant multiple regression result? Explain your reasoning.