The Federal Trade Commission provided measured tar contents (in mg) of randomly selected filtered and nonfiltered king-size cigarettes. A random sample of 21 filtered king-size cigarettes has a mean tar content of 13.3 mg with a standard deviation of 3.7 mg. A random sample of 8 nonfiltered king-size cigarettes has a mean tar content of 24.0 mg with a standard deviation of 1.7 mg. Assuming the two types of cigarettes have unequal variances, test the claim that the mean amount of tar in filtered king-size cigarettes is less than the mean amount of tar in unfiltered king-size cigarettes at a 0.05 significance level.

What should you use for the critical value(s)?

a. -1.65 b. -1.895 b. - 1.96 c. +2.365 d. 1.96 e. 1.65