# Questions tagged [statistical-power]

Is a property of a hypothesis testing method: the probability of rejecting the null hypothesis given that it is false, i.e. the probability of not making a type II error. The power of a test depends on sample size, effect size, and the significance ($\alpha$) level of the test.

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### Sample size calculation for experiment with two treatments [duplicate]

For an experiment I have to calculate the sample size. We want to observe how beliefs affect dishonesty and than add a treatment to see whether beliefs still have an effect when social image concerns ...
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### Calculating sample size with power analysis

I have to calculate the sample size for an experimental study and took some sample distributions data from a previous similar research and calculated the means and standard variations for before and ...
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### One-sided ttests in regression analysis with a clear prior

This question has been asked virtually the same in this post: Regression Slope and a Bilateral Test However, I still don't get my head around why when I have a clear hypothesis of a positive ...
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### How to correctly interpret the results of Power Analysis?

Attached is the result of Power Analysis comparing the means of two independent samples. I am having hard time interpreting the "interpretations" as it is quite convoluted. Does it say the ...
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### Calculate power of 2 sided Z A/B test - pooled version

I want to calculate the statistical power of a 2 sided A/B test where I have 2 groups of coin tosses (that is, from 2 different coins) and their respective successes. I want to test whether the two ...
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### Which statistical model is being used in the Pfizer study design for vaccine efficacy?

I know there's a similar question here: How to calculate 95% CI of vaccine with 90% efficacy? but it doesn't have an answer, at the moment. Also, my question is different: the other question asks how ...
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### Power Analysis for Time Series Models (ARIMA and neural network)

In short, I am building ARIMA (AutoRegressive Integrated Moving Average) and neural network time series (to be more specific, I am using the nnetar() function in R) models to make regression ...
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### Calculate the power of a paired t-test in R manually

As an exercise I wanted to perform a paired t-test manually in R to refresh a lecture I had in the past. Everything went well, but then I thought about calculating the power of this paired t-test and ...
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### Linear mixed model: Does the effect size of an interaction depend on the size of the main effects when size of interaction is kept constant?

Please also see my question here where I describe how I stumbled upon this problem and where I show the respective R-Code. I am running a power simulation where I specify the fixed effects for each ...
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### How to interpret effect sizes in simr power simulation for mixed models?

I am conducting a power analysis for linear mixed models. I want to know what sample size is needed to find a specific effect size for an interaction. I am testing the interaction effect by comparing ...
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### Power simulation (a priori) for mixed models when no prior data is available

The recommended way to do a priori power calculations for linear mixed models is to simulate data and then estimate power using the simr package, for example. All these approaches require you to ...
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### Power test gives power=0.995

I am running a power test for an experiment where I have 122 controls (n1) and 184 experimental sets (n2). I selected a medium effect size of 0.5. I used the pwr.2p2n.test function in the pwr package, ...