On average, do males start smoking at an earlier grade than females? Data from an SRS of 94 12th grade boys that smoke and 108 12th grade females that smoke found that the mean grade of first use of cigarettes was 9.87 for boys (standard deviation of 1.75.) and 10.29 for girls (standard deviation of 1.69). a. Is there sufficient evidence at alpha =.05 that the mean grade for first time cigarette use is different for boys than girls