A research scientist wants to study a certain attribute of dogs. It is estimated

游客2024-01-12  22

问题 A research scientist wants to study a certain attribute of dogs. It is estimated that approximately 5 percent of all dogs have this attribute. If the scientist wants to study a sample of N dogs having the attribute, approximately how many dogs should be screened in order to obtain the desired sample size?

选项 A、N/5.
B、5N.
C、20N.
D、105N.
E、120N.

答案 C

解析 一科学家想研究狗的某种特性。据估计约有5%的狗具有这种特性。若这位科学家想把N只具有这种特性的狗作为一个样本来研究,那么为了得到期望的样本大小,大约需要筛选多少条狗?
解:本题的正确答案为(C)。设需筛选x条狗,则由题意可得:x×5%=N → x=20N
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