The following data refers to airborne bacteria count (number of colonies/ft3

) both for m
8 carpeted hospital rooms and for n
8 uncarpeted rooms (“Microbial Air Sampling in a Carpeted Hospital,” J. Environmental Health, 1968:

405). Does there appear to be a difference in true average bacteria count between carpeted and uncarpeted rooms?

Carpeted 11.8 8.2 7.1 13.0 10.8 10.1 14.6 14.0 Uncarpeted 12.1 8.3 3.8 7.2 12.0 11.1 10.1 13.7 Suppose you later learned that all carpeted rooms were in a veterans’ hospital, whereas all uncarpeted rooms were in a children’s hospital. Would you be able to assess the effect of carpeting? Comment.