6 votes

Why do confidence intervals width increase when sample size increases "a bit"?

A standard confidence interval for a mean is calculated using $s/\sqrt n$. If you increase $n$ but also increase the sample standard deviation $s$ by enough to offset the larger sample size, then your ...
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2 votes

Number of observations for multiple linear regression

For this type of 3-level predictor you only would specify 2 dummy variables and have the 3rd (reference) level represented by having 0s for all the other levels. The reference level is thus ...
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  • 64.4k
2 votes

Sample size calculation for moderated moderation (three way interaction: continuous x continuous x continuous)

The main difficulty with the simulation is that accurate specification of all parameter estimates is difficult as we don't have a good idea of the magnitude of the parameters. I see that as a ...
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1 vote
Accepted

If I need to reduce my sample size due to computation time, should I standardize using my original or post-reduction means and standard deviations?

Likely it should not matter. If taking every 100th point is essentially a random sample from the larger population, the means and variance estimates should be more or less the same. If there is ...
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