filtered cigarettes. Assume that the standard deviation is known = 0.2 milligram. It is believed that the average tar in filtered cigarettes is 1 milligram. To see if this is true, a random sample of 30 cigarettes produced a tar mean of 0.8 milligram. Do you think there is evidence to believe that the mean tar is less than 1 milligram? Use a = 0.05.