申論題

4. (10 points in total) Suppose that the word-association experiment is conducted using eight people as blocks and making a comparison of reaction times within each person； that is, each person is subjected to both stimuli in a random order. The reaction times (in seconds) for the experiment are as follows:

Comment on the use of paired observations to estimate the difference between two population means  rather than estimation based on independent random samples selected from the two populations (unpaired design). Why is a paired experiment often preferable? Explain.