A financial economist is studying married couples in which both spouses work. He wants to compare the mean income earned by husbands with the mean income earned by their wives. Should he use independent sampling or dependent sampling, and why?

(a) Independent sampling. The two spouses are separate people with different jobs, so the husband's income doesn't depend on his wife's income.
(b) Independent sampling. How he selects the husband is independent of how he selects the wife.
(c) Dependent sampling. The husband's income depends to some degree on his wife's income.
(d) Dependent sampling. He needs to select couples for his sample, so whether a particular wife is included depends on whether her husband is included.

The correct answer is letter "D": Dependent sampling. He needs to select couples for his sample, so whether a particular wife is included depends on whether her husband is included.

Explanation:

Two samples are independent if while comparing each one's values the are not related or matched. On the other hand, samples are dependent when the samples of two populations are linked or when one sample of a given population affects somehow the sample of the other.

Thus, in the research conducted by the financial economist dependent sampling must be used because wages of spouses are going to be compared which implies for every husband there will be a wife. Then, the sample of one population is linked with the sample of the other population.