Asimple random sample of 25 filtered 100 mm cigarettes is obtained, and the tar content of each cigarette is measured. the sample has a mean of 19.6 mg and a standard deviation of 3.68 mg. use a 0.05 significance level to test the claim that the mean tar content of filtered 100 mm cigarettes is less than 21.1 mg, which is the mean for unfiltered king size cigarettes. what do the results suggest, if anything, about the effectiveness of the filters?