Question

A researcher thought of another way of studying how smoking affects air pollution in rooms. A random sample of 12 non-smoking rooms were selected and the air quality was initially measured. Then each room got a smoking occupant for a week, and the air quality was measured again after the week ended. Assume that all necessary normality assumptions are met. Below are some summaries:

	mean	standard deviation
sample without smokers	29	35
sample with smokers	86	59
sample of differences	-57	84

The researcher wants to estimate the average change in the air pollution in a room (that was originally non-smoking) after a smoker occupying it for a week. The estimate at 95% confidence level is

Answer 1