问题补充:
单选题在样本的频率分布直方图中, 共有9个小长方形, 若第一个长方形的面积为0.02, 前五个与后五个长方形的面积分别成等差数列且公差互为相反数,若样本容量为160, 则中间一组(即第五组)的频数为A.12B.24C.36D.48
答案:
C解析试题分析:设公差为d,那么9个小长方形的面积分别为0.02,0.02+d,0.02+2d,0.02+3d,0.02+4d,0.02+3d,0.02+2d,0.02+d,0.02,而9个小长方形的面积和为 1,可得0.18+16d=1可以求得d=∴中间一组的频数为:160×(0.02+4d)=36.故