1. Researchers were interested in exploring airway resistance in smokers compared to nonsmokers. They conducted a study to compare the percent of tracheobronchial retention of particles in smoking-discordant monozygotic twins, and the results from the study are provided in the table below. Assume that differences in tracheobronchial clearance constitute a random sample from a normally-distributed population Use these data to answer the questions below the table.

Twin ID	Percent Retention Smoking Twin	Percent Retention Nonsmoking Twin
1-101	60.6	47.5
1-102	12.0	13.1
1-103	56.0	33.0
1-108	75.2	55.2
1-112	12.5	21.9
1-113	29.7	27.9
1-114	57.2	54.3
1-123	62.7	13.9
1-116	28.7	8.9
1-134	66.0	46.1
1-127	25.2	29.8
1-122	40.1	36.2

A. Do these data provide sufficient evidence to indicate that tracheobronchial clearance is slower in smokers? Assume =0.05. Show all of the steps and calculations that you used to arrive at your answer.

B. Calculate the 95% confidence interval for _d and provide an interpretation of the interval.