A researcher wished to test the effect of the addition of extra calcium to yogurt on the "tastiness" of yogurt. Two different yogurts, one with extra calcium and one without the added calcium, were created from the same batch of yogurt. A group of 84 adult volunteers participated in the survey, and 42 were assigned to the extra calcium group and 42 were assigned to the plain yogurt group. The first group tasted the yogurt containing extra calcium and the second group tasted the yogurt without the added calcium. Both groups rated the taste on a 10-point scale with 1 being "very unpleasant" and 10 being "very pleasant."

Identify the design of this study.

A) paired t-test of a mean
B) two-sample t-test of means
C) one sample t-test of a mean
D) one sample z-test of a proportion

B?