Suppose you want to regress household savings on household income, household size, years of education of the head of household, and age of the head of household. Your initial strategy is to estimate a linear regression of this model. For each of the following situations, indicate if this strategy needs to be modified and, if yes, how you would modify it. Include a brief explanation for each.

a. Your sample consists only of families whose head is over age 25.

b. Your sample consists only of childless married couples.

c. Your sample has excluded all families that save more than $20,000.