题目
题目

stat_400_120258_253926 PA12-5

单项选择题

When should we used pooled variance for a test of two sample means?

选项
A.Only when the population variances are unknown
B.Only when conducting hypothesis tests
C.Only when the population standard deviations may be assumed to be equal
D.Only when the population variances are known
E.Only when calculating confidence intervals
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思路分析
Topic focus: using pooled variance in tests comparing two sample means. Option 1: 'Only when the population variances are unknown' — this is not precise. The decision to pool variances is about whether the variances are equal, not merely whether they are known or unknown. Even if variances are unknown, pooling is not automatically appropriate; unequal variances suggest not to pool. So this statement is misleading. Option 2: 'Only w......Login to view full explanation

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