This paper studies the second stage sampling methods used in the two stage sampling survey for waterway transportation volume.
研究了采用二阶抽样对水路运输量进行抽样调查时的第二阶抽样方法。
Because of its large volume and low cost, the waterway transportation occupies a large share in the transportation of dangerous goods.
水路运输因其运量大、成本低等特点在危险货物运输中占据了较大份额。
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