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We give the approximation formulas of the variance of the sample ratio estimator for a population mean and its asymptotically non-biased estimator in multi-stage sampling.
讨论多阶段抽样比率估计及其样本量选择的问题，给出了比率估计抽样均方误差的近似公式及其渐近无偏估计的公式。
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Microsoft hotly contested this, and claimed Mr Weadock's sampling was biased.
BBC: USA versus Microsoft: The fifth week
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