1.Two brands of cigarettes are selected, and their nicotine content is compared. The data are:

Brand A X1 = 28.6 mg; s 1 = 5.1 mg; n1 = 30

Brand B X2 = 32.9 mg; s 2 = 4.4 mg; n2 = 40

Is there convincing evidence that the mean amount of nicotine differs between the brands?