8.为了解某校初三毕业班学生数学成绩的分布,随机地抽查50名初三学生进行测-|||-试,得到分数如下-|||-58,92,69,67,84,94,57,74,74,83,51,62,64,62,67,72,68,92,84,82,70,87,78,75,60,-|||-78,81,67,77,85,76,66,72,78,82,63,74,98,68,73,72,80,86,73,79,66,87,77,88,78.-|||-(3)以组中值d(第i组的组中值)为代表,计算平均值 overline (x)=sum _(i=1)^10(n)_(i)(d)_(i)/50. 在实际工作中,-|||-常可以x作为x的近似值.