加权平均数的计算公式

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\bar{x}=\frac {{x}_{1}{\omega }_{1}+{x}_{2}{\omega }_{2}+\cdots +{x}_{n}{\omega }_{n}} {{\omega }_{1}+{\omega }_{2}+\cdots +{\omega }_{n}} \\ \bar{x}=\frac {{x}_{1}{f}_{1}+{x}_{2}{f}_{2}+\cdots +{x}_{n}{f}_{n}} {n}

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