A statistical measure of the variance of two random variables that are observed or measured in the same mean time period. This measure is equal to the product of the deviations of corresponding values of the two variables for their respective means.

• 协方差在观察或测量同一平均时间的两个任意变量的变化的一个统计值。这个值等于这两变量的各自平均值偏离其相应值的乘积