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9 votes
Accepted

Estimate random effect variance for power analysis in multilevel model

There are no absolute guidelines, but for instance Arend & Schäfer (2019) suggest, based on their literature review yielding average ICC of .30 that ICC = .30 could be considered a medium-sized ...
Sointu's user avatar
  • 2,333
7 votes

Estimate random effect variance for power analysis in multilevel model

To add onto Sointu's excellent response, you should be looking at longitudinal studies on the construct (or related constructs) of interest in your project. This will give you a sense of the size of ...
Erik Ruzek's user avatar
  • 5,145
5 votes
Accepted

What is the interpretation of alpha and beta within the plots of a H0 and H1?

The graph is correct, but probably more confusing than it is helpful. The 2 gaussians are meant to represent 2 different scenarios: the first, when $H_0$ is true (sampling distribution 1), the other, ...
jginestet's user avatar
  • 1,002
5 votes

Multinomial logistic regression sample size

There are two reasons I can think of to be working on a sample size: 1) Power and 2) Avoiding overfitting For Power: I don't know of a prepackaged program to do power analysis for multinomial logistic....
Peter Flom's user avatar
  • 122k
4 votes
Accepted

What does it mean to run a power analysis for one variable in a multiple logistic regression?

I need to try to show that the study is underpowered to detect effects from this predictor. You can't determine the power of a study post hoc, but you can determine the power for similar studies that ...
Demetri Pananos's user avatar
4 votes
Accepted

Why is there such is difference in sample size estimation between Lehr's method and Statsmodels

The formula you give (what you call Lehr's formula) is for a two-sample t-test comparing two groups. In contrast the [statsmodels.stats.power.TTestPower function is ...
Björn's user avatar
  • 33k
3 votes
Accepted

Power analysis for ANCOVA

how in practice might one compute the power of an experimental design where the covariates have already been identified and ANCOVA is the intended inference algorithm? First, let's discuss equations ...
Demetri Pananos's user avatar
2 votes
Accepted

Effect size/power analysis of categorical variable in multilevel model

The important part, as Sointu notes and is part of your question, is that you need to get a sense of what the previous research says the effects should be before running such analyses, and this can ...
Shawn Hemelstrand's user avatar
2 votes

F test to compare variances. How is ncp calculated to obtain the F distribution under the alt hypothesis?

The non-central $F$ distribution is the alternative-hypothesis distribution for ANOVA or regression, not for the test of equality of variances. That is, it is the distribution of the ratio of sums of ...
Thomas Lumley's user avatar
1 vote

Why is there such is difference in sample size estimation between Lehr's method and Statsmodels

Your problem statement has a few issues. First, the Lehr's rule is an approximate formula, not an exact one. But that would not explain such a large difference in estimated sample sizes. You state &...
jginestet's user avatar
  • 1,002
1 vote

Reviewer wants "post-hoc" power analysis for a mixed effect model

Sorry to leave you hanging. So, as we all know, post-hoc power analyses are useless. However, if a reviewer demands one and you want to do it in order to get forward in the publication process, your ...
Sointu's user avatar
  • 2,333
1 vote
Accepted

Interpreting the result of post hoc power calculation with powerCT.default for proportinal hazards model

I don't know how to calculate power/sample size for proportional hazards model because I don't use them. But generally, to conduct a priori power calculations for a simple design, you need to provide ...
Sointu's user avatar
  • 2,333
1 vote

Power of Test in a Coin Toss Experiment

In your example, $H_A$ is a composite (rather than simple) hypothesis. In this case, we have to ask what exactly does it mean for $H_A$ to be true? The power here will be a function of the true value ...
knrumsey's user avatar
  • 8,247
1 vote

Multinomial logistic regression power analysis

Pate et al. propose a method for conducting a power analysis for multinomial logistic regression in a recent publication: Pate, A., Riley, R. D., Collins, G. S., van Smeden, M., Van Calster, B., Ensor,...
filups21's user avatar
  • 395
1 vote

Power analysis for multinomial logistic regression

Yes, you can use multinomial logistic regression to predict a categorical outcome with a continuous predictor. Power analyses for multinomial logistic regression are complex, but possible. Here is a ...
filups21's user avatar
  • 395
1 vote

How to compute the power of Wilcoxon test?

Power calculations that are completely tailored to the Wilcoxon-Mann-Whitney two-sample rank-sum test for both discrete and continuous (normal and non-normal) data may be found here and here. ...
Frank Harrell's user avatar

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