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【判断题】
连续精馏塔的塔顶和塔底产品分别为D和W，则精馏段液汽比总是小于1，提馏段的液汽比总是大于1。A.
正确
B.
错误
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【多选题】Which of the following statement about quota sampling and stratified sampling is/are true?
A.
In both of them, there exist distinctive subgroups in the population.
B.
They both need a sampling frame of each of the subgroups of the target population.
C.
In both of them,researchers want to ensure that all strata are included in the sample in order to enhance the representativeness of the sample and/or to enable comparisons between strata.
D.
Stratified sampling does not need a sampling frame to generate a stratified sample.
E.
In both of them,once the sample number of each subgroup is defined, samples are drawn in simple random sampling or systematic sampling method.
【单选题】______________ sampling is a form of probability sampling in which sampling units are divided into mutually exclusive and collectively exhaustive subpopulations.
A.
Judgment sampling
B.
Quota sampling
C.
Simple random
D.
Convenience
E.
Cluster
【简答题】C套传票 行次二 页码:8页至17页
【简答题】有人说:“电容器带电多电容就大,带电少电容就小,不带电则没有电容。”这种说法对吗?为什么?
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