2. Two random samples of 8 and 11 plots are chosen independently from two distant places. The yields of maize obtained from these plots are given below. Test whether the average maize yield is same for two places. (15 points)
First place: 12, 15, 16, 11, 13, 13, 14, 15
Second place: 15, 22, 12, 25, 18, 19, 20, 17, 25, 24, 18