APFIVE Standard Error and Sample Size
An initial experiment with 20 subjects reports a standard error of $$2.5$$ for the measured response variable. If the experiment is replicated with 80 subjects, what is the expected standard error of the mean, assuming the individual variance remains unchanged?
Replication and Standard Error:
| Sample Size | Observed Standard Error |
|---|---|
| 20 | 2.5 |
| 80 | ? |
Assume the variance remains constant when the study is replicated with a larger sample size.
A
$$2.5*\sqrt{20/80} = 1.25$$
B
$$2.5/2 = 1.25/2$$
C
$$2.5$$
D
$$5.0$$
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