It is commonplace to gain weight after quitting smoking. Does the drug Naltrexone help limit weight gain when individuals quit smoking? To determine the effectiveness of this drug, 147 subjects who smoked 20 or more cigarettes daily were randomly divided into two groups. Everyone received a 21-milligram (mg) transdermal nicotine patch (to curb nicotine cravings while trying to quit smoking). Seventy-two subjects received a placebo, while 75 received 25 mg of Naltrexone. After 6 weeks, the placebo subjects had a mean weight gain of 1.9 kg, with a standard deviation of 0.22 kg; the Naltrexone subjects had a mean weight gain of 0.8 kg with a standard deviation of 0.21 kg.
Construct a 95% conﬁdence interval for the mean difference in weight gain for the two groups. Based on this interval, do you believe that Naltrexone is effective in controlling weight gain following smoking cessation? Do the results have any practical signiﬁcance?