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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Bootstrapping as an alternative to simulation-based power/sample size calculations
Typically when one has to do a sample size and/or calculation, they might use simple sample size calculations from textbooks or use gpower. However, there are only closed form calculations for very ...
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How can I convert an effect size from Cohen's d to f(v)
I am interested in calculating the power I need to compare several groups to one reference group in how much an outcome changes between two timepoints. My understanding is that I should use the ANOVA: ...
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Logistic regression sample size with categorical predictor in G power
I am trying to figure out if G power is the way to go in my case and if I am doing it right. I wish to calculate a priori sample size.
I am about to do a cohort study using registry data using ...
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Calculating sample size based on a 2 x 2 x 2 repeated measures ANOVA using G Power
I am planning on doing a 2 (A: a1, a2) x 2 (B: b1, b2) x 2 (C: c1, c2)repeated measures ANOVA where A and B are within subject factors and C is a between subject factor.
In G Power, I suppose the &...
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Guidance on running G*Power to calculate the sample size using Poisson Regression
I am working on a dissertation to determine if there is a difference in the number of specific disciplinary actions (5 count dependent variables) from before remote learning and after remote learning (...
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Sample size estimation using G*Power
I am trying to calculate an a priori sample size using the G*Power for a project that I intend to do. I will collect reaction time data from two groups of participants across two time points (T1, T2). ...
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Mixed ANOVA Power Analysis
So I'm doing a thesis on compassion meditation and I'm confused about the power analysis. When I calculated it in G*power, "total sample size= 34", but it's for a 2x2 mixed ANOVA, so does ...
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Predictor variables vs control variables for power analyses in multiple regression G*Power
I am using GPower to get an idea of the sample size needed to detect a medium effect size in the second and third steps of a hierarchical multiple regression model. To do this, GPower asks for the ...
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How do I to correct the α in the power analysis？
The reviewer asked us to use a corrected α when calculating the sample size with G*Power.
The literature I found suggests that the Bonferroni adjustment = α/n (Armitage, Peter; Colton, Theodore, 2005)....
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G*Power sample size calculation between regression coefficients in two separate within-subject models
I have two identical regression models run on two different subsamples. In R, my models would be the following:
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Power of One Sided t-test
Let $X_1, \ldots, X_n$ be a sample from $N(\mu, \sigma^2)$ for unknown $\mu \in \mathbb{R}$ and unknown $\sigma > 0$. Fix $\mu_0 \in \mathbb{R}$. The one-sided hypothesis is $H_0: \mu \leqslant \...
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G*Power Mixed two-way ANOVA power analysis - sample size seems too small? [duplicate]
I am running my first-ever power analysis and I am worried that I am misunderstanding something about G*Power. I am running a 2x2 mixed ANOVA. I chose the 'ANOVA: Repeated measures, within-between ...
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Approximate power analysis for simple linear mixed model without random effects
For educational purposes, a repeated measure of all participants in two conditions is modeled as linear mixed model. We're interested in the difference in outcome while controlling for confounders $...
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sample size calculation using G*Power -- which model to use based on an already calculated effect size?
I want to perform a sample size calculation using G*Power. I have 2 predictors and want to test how these 2 predictors affect change over time in a specific cognitive measure. The cognitive measure ...
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Help: G*Power Analysis for Correlation and Moderation
I have 3 measures, all scored on Likert style scales and I will be using the sum of items from each as scores. It is a cross-sectional study. predictor variable is attachment style (with two levels, ...
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Statistical power of my study
I am writing a paper for a journal. I have been asked to calculate the statistical power of my study. I have zero idea about how to do that. I am an engineer and never cared about this kind of ...
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Repetitions on the same combination of factors in mixed ANOVA and its power analysis
I am trying to decide the appropriate model and perform power analysis. Suppose a data contains 2 groups (A,B) and 28 participants from each group. All of those participants are measured 15 times on ...
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Power Analysis for 8x8 factorial within-subjects design (required number of participants/samples)
for an experiment, I was asked to provide a minimum required number of participants using an a-priori power analysis. Thing is, I'm now really confused on how this is possible or even if it makes ...
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How does G*Power calculate sensitivity in z-test for two independent proportions
I am trying to recreate sensitivity calculation in Python by applying the same methodology as used in G*Power
z-tests > Proportions: Difference Between Two Independent Proportions > Sensitivity: ...
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Is G*Power reliable for logistic regression? It does not seem to account for Hauck-Donner
I've just been introduced to G*Power. The only option I could find for analysing logistic regression is described as:
Options: Large sample z-Test, Demidenko (2007) with var corr
That seems to ...
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Sample size calculation for RM ANOVA; the difference between WebPower package in R and G*Power 3.1.9.7
I've run two sample size calculations with the WebPower package in R and G*Power simultaneously.
The conditions I've done are;
Case 1
Cohen's f = 0.2756987
Number of groups = 1
Number of repeated ...
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Would a post hoc power analysis be used for a retrospective chart review and how would this be done?
I'm a novice in research and wondering if I need to calculate power to determine my sample size. My study is about collecting data from all patients that presented to a clinic for a period of 6 months....
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How to interpret a sensitivity analysis from G*Power for a repeated measures, within factors ANOVA
I am trying to conduct a sensitivity power analysis for a (2x2) ANOVA. The participants all received trials based on color or shape, and items could be either old or new. In G*Power I have the ...
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Sample Size Question - Population- Multiple Regression?
I am doing a research project for class. Our research questions are as follows:
Has news exposure impacted parental decision-making in preparation for the new school year?
Has Media exposure to ...
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Post hoc power analysis options for 2x2 ANOVA and paired t-tests
We recently submitted a manuscript for publication. My advisors never do power analyses, and so the reviewers came back questioning our sample sizes. Lesson learned on my end. One reviewer said "...
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G*Power repeated measures ANOVA within-within interaction
Suppose that I have 4-by-6 factorial design where both factors are within-subject variables, and I want to perform a repeated-measures ANOVA on the data. Using GPower, I calculate the sample size ...
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G Power Settings for Friedman Test Comparing Multiple Models
UPdated to convey statistical question:
The underlying statistical question is one of which test to use: I have three models against a single dataset. I want to see which model is better. Is repeated ...
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G*Power ANOVA repeated measures within-between interaction
I'd love to get a sanity check on a sample size calculation I'm running in G*Power. I'm planning a study with 2 groups and 2 measurement points, aiming for a f of 0.10 because, to my understanding, it'...
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Power Analysis for 2-Way-Anova in R
I did a power analysis to calculate the sample size in GPower.
Now I'd like to do the same in R. However, I am not able to figure out how...
I found ss.2way but that seems to require different inputs.
...
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Determine the sample size to validate a bug fix
Using gpower, I would like to calculate the sample size to validate a bug fix.
There is a software bug that appears in 3 out of 1000 test runs.
I would like to validate a bug fix so that it doesn't ...
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Statistical power and sample size for Poisson regression: specifying the "mean exposure"?
I am trying to perform an apriori power analysis to estimate sample size for a Poisson regression model. The background is that a RCT is proposed to compare the rate of pill consumption between two ...
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G*Power - Difference between ANOVA Repeated measures, between factors and ANOVA: Repeated measures, within-between interaction
I have a mixed-ANOVA design: 2 groups (experimental & control) x 4 time points (pre, post, post2, post3), and am using G*Power to calculate the required sample size.
My understanding is that the &...
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Reviewer is requesting the use of Bonferroni adjustment to alpha in G*power calculation ("multiple regression" with 3 predictors)
Since Bonferroni is intended as a (conservative) adjustment to reduce Type 1 error, I'm unclear why it would be required by the reviewer to adjust alpha in the power calculation (using G*power). While ...
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GPower: unequal number of measurements?
I'm in psych research, so typically I have my subjects do ~40 trials per condition. If I have an uneven number of trials per condition (say, 30 in one and 40 in another) and a 2 x 2 within-subjects ...
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Multiple linear regression: minimum sample size required when only a subset of independent variables are of interest
I am planning a multiple linear regression model with 1 continuous dependent variable and 6 independent variables. Of these 6 independent variables, I am only interested in the contribution of 2 ...
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Why are ztest and chisquared test not returning equivalent sample size results?
I'm using the statistical software G*Power to find the minimum sample size needed to detect whether or not the difference in two proportions is statistically significant in an AB test I'm setting up. ...
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What are the distribution values (mu, sigma) for alternative hypothesis of differences between two proportions? How to calculate?
When comparing two independent proportions (p2, p1) in an A/B test, null hypothesis states that the difference is 0, while the alternative hypothesis states it is something other than 0, let's say mu1....
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Noncentrality parameter Repeated-Measures ANOVA - formula vs. G*Power
I am trying to figure out the correct expression for the noncentrality parameter $\lambda_{ws}$ for the within-subjects effect in a one-way Repeated-Measures ANOVA with $k$ trials/groups. Comparing ...
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Formal name for research design: repeated measures, 1 varying treatment condition, 1 constant treatment condition
I'm coming from a background with regards to randomizing treatment and just conducting measurement at one point in time. In my current setup, there are just four groups of interest: A control group (C)...
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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 ...
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Power analysis without a prior and for observational data
I am trying to develop the design for an observational study, but I am struggling with the number of observations that would allow us to estimate our model and generalize its results. As a dependent ...
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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 ...
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ANOVA Repeated Measures crossover design, number of measurements in GPower?
I am planning an experiment in which I will have a group of animals which I will give both the control diet also test them on the treatment diet.
I think I can use repeated measures ANOVA for this. I'...
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What does Actual α mean in G*Power?
Can anyone explain what actual α (alpha) means in G*Power?
For input parameters, I choose 0.05 for α err prob, and I get 0.0288167 for Actual α.
Does it mean I should use 0.0288167 instead of 0.05 for ...
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GPower: Difference in Sample Size for ANCOVA vs. Repeated Measures ANOVA in clinical trials
I want to conduct a randomized pre-post intervention study with two measurement points (1. Baseline 2. Post-intervention) and two groups (Treatment vs. Control) and am currently trying to work out the ...
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Regression power analysis: R's `pwr::pwr.f2.test` R2 deviation from zero vs. R2 increase (vs. G*Power)?
This question is about the difference between R's pwr::pwr.f2.test and G*Power regarding the ...
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Numerator degrees of freedom in power analysis for regression (R vs. G*Power)
Background
In R, the power analysis package pwr can estimate the required sample size for regression with the following formula:
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Power analysis: Use a prio test to determine number of particants with G*Power
I would like to conduct a priori power analysis to determine the number of required participants for my experiment. I want to have two experiment groups (with immersive and desktop virtual reality) ...
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Sample Size - GPower options in F tests, ANOVA: Repeated measures, within factors
I'm trying to determine sample size and found that the "Options" in G*Power 3.1.9.7 changes the effect size (seems to automatically convert this and provides the same results, first two ...
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Power Calculations for Diff-in-Diff with Fixed Effects
I am conducting a field experiment. Where we observe two different optimization methods.
First 7 days pre-treatment period and 28 days treatment period.
To split treatment and control, we will have ...
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