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【简答题】
用简单随机重复抽样方法抽取样本单位，如果要使抽样平均误差降低50%，则样本容量需要扩大到原来的（ ）倍。
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【单选题】A. aboard, B. mission, C.attach He regards learning as a daily experience as well as a lifetime _____.
A.
aboard
B.
mission
C.
attach
【单选题】在填料层高度为 3.5m 的萃取塔内用纯水提取乙醛和甲苯混合液中的乙醛,原料液中乙醛的质量比组成为 0.053 ,要求乙醛的萃取率为 85% ,操作条件下水和甲苯可视作不互溶,且以质量比表示相组成的分配系数 Ka=2.2. 操作溶剂比( S/B )为 0.455, 。则操作溶剂比与最小溶剂比比值为( )
A.
1.178
B.
1.781
C.
1.871
D.
2.2
【单选题】If the elasticity of supply coefficient for a good is one-sixth (in absolute terms), we know:
A.
that for every 1% increase in quantity, there will be a 6% increase in price.
B.
that for every 1% increase in quantity, there will be a 6% decrease in price.
C.
that for every 6% increase in quantity, there will be a 1% increase in price.
D.
that for every 6% increase in quantity, there will be a 1% decrease in price.
【单选题】拟用萃取方法提取丙酮水溶液中的丙酮。原料液的处理量为120kg,其中丙酮的质量分率为0.3。萃取剂为纯氯苯,总量为100kg。在操作条件下,水和氯苯可视作完全不互溶,且以质量比表示相组成的分配系数平均值为K=1.25。单级萃取时丙酮的萃取率是()。
A.
0.597
B.
0.671
C.
0.654
D.
0.683
【单选题】Suppose that in a particular economy, the multiplier is equal to 5. In terms of aggregate demand and aggregate supply, this value for the multiplier means that after an increase in investment (假设在特定的...
A.
at each level of real GDP, the aggregate demand curve shifts upward by an amount equal to 5 times the change in investment.在实际GDP的每个水平上，总需求曲线向上移动等于投资变化的5倍。
B.
at each level of real GDP, the aggregate supply curve shifts upward by an amount equal to 5 times the change in investment.在实际GDP的每个水平上，总供给曲线向上移动等于投资变化的5倍。
C.
at each price level, the aggregate supply curve shifts rightward by an amount equal to 5 times the change in investment.在每个价格水平，总供给曲线向右移动等于投资变化的5倍。
D.
at each price level, the aggregate demand curve shifts rightward by an amount equal to 5 times the change in investment.在每个价格水平，总需求曲线向右移动等于投资变化的5倍。
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