The technical definition of variance is the random variable's second central moment, the weighted average of the square of the differences from the expected value.

3方差的专业定义是随机变量的二次中心矩，与期望值之差的平方的加权平均值。

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Some parameters chain may deviate from the expectancy value or average in the supply chain, such as demand, price, cost, and so on, and then there is a variance risk.

供应链中的某些参数，如需求、价格、成本等可能偏离供应链的预期值或者平均值，这就产生了供应链方差风险。

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The results show that the average value of tracheid form can not be affected by the planting density through variance analysis .

结果表明，造林密度对马尾松管胞形态总平均值影响不大，方差分析不显著；

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