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方差是刻画一组数据偏离平均数程度的一个基本量,它反映了一组数据的波动情况.方差越大,数据的波动越大;方差越小,数据的波动就越小.表现在图象上,方差越小,代表数据的点越密集;方差越大,代表数据的点越离散.方差的计算公式是s~2=1/n·[(x_1-x)~2+(x_2-x)~2+…+(x_n-x)~2].在学习中,我们不仅要牢记公式.而且还要注意它的一个简化公式以及相关性质的应用.
Variance is a basic quantity that characterizes the deviation of a set of data from the average, which reflects the fluctuation of a set of data. The larger the variance is, the larger the data fluctuation is; the smaller the variance is, the smaller the data fluctuation is. On the other hand, the smaller the variance, the more dense the points representing the data. The larger the variance, the more discrete the points representing the data. The formula for calculating the variance is s 2 = 1 / n · [(x_1-x) ~ 2 + (x_2-x ) ~ 2 + ... + (x_n-x) ~ 2] In learning, we should not only keep the formula in mind, but also pay attention to its simplification formula and the application of the related nature.