Variance s a 2=(78? 84)2+(8 1? 84)2+(84? 84)2+(85? 84)2+(84? 84)2+(85? 84)2+(9 1? 84)27=967;

B the average score of athletes. x B = 79+84+84+86+87+84+9 17 = 85，

Variance s b 2=(79? 84)2+(84? 84)2+(84? 84)2+(86? 84)2+(87? 84)2+(84? 84)2+(9 1? 84)27=807;

∵807