Suppose that a scientist seeks to compare the ability of a new hand sanitizer to eliminate Pseudomonas aeruginosa bacteria against the hand sanitizer currently in use. Assume that the mean number of bacteria remaining on a hand after using sanitizer is approximately normally distributed; however, the population standard deviation is unknown. The scientist selects a simple random sample of 57 students. Each subject uses the new hand sanitizer on one randomly‑chosen hand and the sanitizer currently in use on the other. The number of Pseudomonas aeruginosa bacteria remaining on each hand after using the sanitizers is determined, and the difference in the number of bacteria on the hand treated with the new sanitizer and the number of bacteria on the hand treated with the current sanitizer is determined.

Choose the procedure for estimating the mean difference.

A. two sample test for a difference in means

B. one sample confidence interval for paired data

C. two sample confidence interval for a difference in means

D. one sample confidence interval for a difference in means

E. one sample test for paired data