Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [gpower]

G*Power Statistical Power Analyses for Windows and Mac is a program which helps with calculating the power of some statistical tests.

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Power of interactions in factorial ANOVA using G*Power

I’m using GPower to perform a priori power analysis. Let’s say that I want to do a 2x2 factorial ANOVA. I’m interested in the power of the interaction. I set effect size f to .25, alpha value to .05, power to .80. The degree of freedom of my…
Marc
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What are appropriate statistic tests for top-down and bottom-up knockout experimental designs?

This concernes a two staged experiment on cell toxicality. A: Aim is to find the lowest concentration of the toxic agent 'CTA', that kills the target cells with at least 99% security. Use of lowest effective concentration is to be preferred and the…
ABri
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Is it possible for power (1-B) to equal 1?

I'm using a program called GPower to calculate the achieved power of a certain test I've performed. Below is the screen shot of my inputs and outputs. It states that my test achieved a power of 1.0 - meaning there is a ZERO percent chance of a Type…
Nicholas Hassan
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How to work out Effect Size for a MANOVA using G*Power

I'm using G*Power to work out how many participants I need. I'll be using a MANOVA, I have two independent variables (Male and Female) and they will be answering 13 different questionnaires so 13 dependent variables. I put this data into G*Power…
Jesse Smith
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ANCOVA controlling baseline in RCT - power analysis and sample size questions

I am performing a power analysis/sample size estimation for an RCT. We will be controlling for baseline symptoms and using post-treatment or change scores as our outcome variable. This design is referred to as "ANCOVA" and designs with these…
LJN
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Power calculations

I am using a toy example to explain power calculations for a t-test Let's say we have two populations where we measure a certain parameter. Population A has a mean of 0 and population B has a mean of 3, both with a sd of 2. The effect size is 1.5 I…
nico
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Power analysis for same model as "ANOVA" vs as "multiple regression" yields different results

I have seen posts that said ANOVA and multiple regression are theoretically the same. But if this is really the case, does anyone know why the G*Power (Linear multiple regression vs ANOVA) gives massively different sample sizes with the same/similar…
user240313
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When planning to use Multivariate Regression with some binary categorical predictors, how do I find the sample size I need using G* Power?

I want to run a multivariate regression data analysis. I have 5 predictors--two of them are binary--and one DV. When planning to use Multivariate Regression with some binary categorical predictors, how do I find the sample size I need to justify…
Axelbrain
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Calculate required sample size for multiple linear regression

I'm planning to run a survey experiment where I have a pre-measurement of my outcome variable, then I'm randomly assigning my respondents to one of six treatments/stimuli ("NO" = baseline group, Tier A, Tier B, Tier C, Premium 1, Premium 2) followed…
deschen
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Why is the sample size calculation not in agreement with t-test results?

I used R package pwr (G*Power gives the same result) which say for a one-sided t-test of means with alpha=.05, beta=.20, that I would need 40 samples for both control and treatment groups (n=80) to detect a 35% reduction (corresponding to effect…
StatsNTats
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Power analysis for one way anova with post hoc Tukey?

I have an experiment in which I'm doing, among other things, a One way Anova with one dependent variable and 5 groups. After the ANOVA i'm doing Tukey's post hoc to test for differences between groups. I want to conduct a power analysis to determine…
Gonzalo Lerner
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ANCOVA vs multiple regression the same: so why different power analysis results?

This is a general question so I am not supplying details of my experiment. When I search for information on whether to conduct ANCOVA/ANOVA or multiple regression, in many sources including this forum people say they are "the same thing". Yet when I…
ambalashes
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Carry out power analysis for MANCOVA using G*Power

There are helpful questions and answers for how to calculate the required sample size (or carry out a power analysis) for MANOVA, but not for MANCOVA using the freely-available G Power software. Is there a way to do so for MANCOVA using G*Power?…
Joshua Rosenberg
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a priori power analysis for ANOVA plus post hoc test

I would like to perform an a priori power analysis to calculate required sample size for data to be analyzed using one way ANOVA and Tukey HSD post hoc test. (I want to determine pair-wise which groups are different from each other) desired…
jlarsch
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Is there any way to do a power-based sample size calculation if you don't know the minimal (scientifically) important difference?

I am in the life sciences field and I don't have much experience with power-based sample size calculations. I am doing a Western blot experiment and my research question is whether protein X influences the levels of protein Y during development. In…
ceno980
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