Aijing Shang wrote:
>Dear all,
>Recently when I calculate power using sampsi, a strange thing happened. I
>want to compare two proportions, one is 0.001, another is 0.002. As what I
>know, the bigger the sample size is, the more power it is. However, the
>results sampsi gave are reversed. See the results following.
>. sampsi 0.001 0.002, n1(10) n2(10) alpha(0.05)
>Estimated power:
power = 0.9999
>. sampsi 0.001 0.002, n1(100) n2(100) alpha(0.05)
>Estimated power:
power = 0.3762
>. sampsi 0.001 0.002, n1(1000) n2(1000) alpha(0.05)
>Estimated power:
power = 0.0250
>Can anybody tell me what is wrong? Thank you very much.
In addition to my previous answer:
We've spent some more time looking carefully at the -sampsi- command today.
In a future update -sampsi- will display a warning message in the case when
the approximation to normality of the test statistic for proportions is
doubtful.
--Yulia
[email protected]
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