Method National system sampling survey of kinds and number of the equipment in institution of disease prevention and controlment, compute equipment assets, and gaps compare with standard.

方法全国系统抽样调查省市县各级疾病预防控制机构的各类设备配置种类和数量，计算设备资产，和标准比较得到缺口。

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It revealed that the product of the standard deviation of the estimated sampling variance and square root of the number of samples was a constant.

实验也证明，取样方差估计值的标准偏差与样本数目的平方根之积可近似为一常数。

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