Each situation described bellow requires inference about a mean or means. identify each as involving (1) a single sample, (2) matched pairs, or (3) two independent samples.

1- looking back on love. choose 40 romantically attached couples in their midtwenties. interview the man and woman separately about a romantic attachment they had at age 15 or 16. compare the attitudes of men and women.

2- chemical analysis. to check a new analytical method, a chemist obtains a reference specimen of known concentration from the national institute of standards and technology. she then makes 20 measurements of the concentration of this specimen with the new method and checks for bias by comparing the mean result with the known concentration.

3- chemical analysis, continued. another chemist is checking the same new method. he has no reference specimen, but a familiar analytic method is available. he wants to know if the new and old methods agree. he takes a specimen of unknown concentration and measures the concentration 10 times with the new method and 10 times with the old method.