同学们知道用极差描述数据的离散程度简单明了,但由于极差仅仅由其中的最大值和最小值所确定,个别远离群体的极端值会在很大程度上影响极差,因而极差往往不能充分反映一组数据的实际离散程度.而方差能非常精确地反映一组数据的离散程度,用方差不仅可以用来解决实际问题,而且还是中考的热点问题.一、直接给出方差,判断稳定性例1甲、乙两个参加市组织的省“农运会”铅球项目选拔赛,各投掷6次,记录成 Students know that dispersion is straightforward to describe data in terms of range, but since the range is determined by only the maximum and minimum values, the individual extreme values ​​that are far from the population can have a large impact on the range and the range is often Can not fully reflect the actual dispersion of a set of data.While the variance can very accurately reflect the degree of dispersion of a set of data, with variance can not only be used to solve practical problems, but also the hottest questions in the test. Stability Example 1 A, B two participating cities organized by the provincial “Farmers Games ” shot put the project trials, each throwing 6 times, recorded as