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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 clinical trial

I am trying to replicate a study about a randomized clinical trial. For this purpose I want to obtain the sample size calculation the authors did. In the paper they say: Assuming a reduction of the ...
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Power analysis for the Cox proportional hazards model

I'm trying to work out the sample size needed for an RCT based on a small study looking at reoperation following index surgery. In this small study, there were 1000 patients, group 1 had 700 versus ...
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Issues with Detecting Negative Change in AR(1) Model Using CPAT Library

I'm currently working on evaluating the empirical power of the CUSUM, Rényi CUSUM, and Erdős-Darling tests for detecting change points in AR(1) models, specifically focusing on changes in the mean. ...
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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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R: How to calculate power to detect a change in mean beta reg.?

I'm interested in calculating the power to detect a change in my mean response variable by a certain effect size, but I'm not sure how to start. My Y variable is mean plant cover 0-100% cover (mean of ...
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How to do a power analysis on density (count/area) data?

I would like to calculate the power to detect a hypothetical x% decrease from a mean value, but have a few qualifying questions. The data are strictly positive, right-skewed, continuous data ...
Nate's user avatar
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Two-Way repeated measures ANOVA with multiple data points per measurement

I would like to perform a study with physicians of three levels of experience. They shall perform a task under three different conditions. For each condition, the task is performed multiple times (e.g....
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How to combine intention-to-treatment randomization with block randomized experimental designs for within-differences in Power Analysis

I want to calculate the power for my experiment. Within multiple blocks of similarities (e.g., same gender, same pre-treatment outcome), respondents get the opportunity to take part in a treatment. As ...
canIchangethis's user avatar
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is the likelihood ratio test "best" for finite samples?

Wikipedia says The Neyman–Pearson lemma states that this likelihood-ratio (lr) test is the most powerful among all level α alpha tests for this case. Is this only true for infinite sample sizes? Is ...
A Friendly Fish's user avatar
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Chi-square power with (heavily) unbalanced proportions

I want to calculate the statistical power of a chi-square test with (heavily) unbalanced proportions. I have a variable that I analysed for a sample and whose distribution I know in the population, ...
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Power estimate for an interaction term in factorial design

I am trying to estimate power for a factorial design (2x2). My initial approach was to estimate pair-wise minimum detectable effect sizes : i.e., if I know sample size, allocation to each group and ...
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Why should you want to use a smaller control group?

In an RCT with multiple treatment arms, I heard that the "pure" control group be small to if we expect the effect size to be large. Why would this be the case? I understand that we could ...
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How to perform a power analysis for poisson distributed data

I want to perform a simplified power analysis to determine how many cells (samples) to have in control and experimental conditions (assume equal n across conditions). For an alpha level of 0.05, 0.95 ...
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z score total for fixed alpha and beta in sample size calculation of mean differences

Can someone explain in detail how $z_\text{total}=z_{\alpha} + z_{1-\beta}$ in a one-tailed hypothesis test of mean difference $\mu_1 - \mu_2$ with common variance in order to determine sample size. ...
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Power calculation with a binary outcome (using a R package & manual simulation)

I am trying to compare three different methods for power calculation under the same setting. Although I understand that the power estimates from each method cannot be exactly identical due to ...
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Likert scale and sample size

I want to study the satisfaction of a mother receiving paper or website information. I will have at least 5 questions, with Likert scale (5 points) each time. For the sample size: Should I calculate ...
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Sample size calculation for Cox regression for comparison of four treatment groups

I need to calculate the required sample size for a future study. We have 4 treatment groups, one of those will be the control group. The goal is to compare each of the 3 treatment groups to the ...
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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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2 answers
121 views

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

I have been using Lehr's rule to estimate the required sample sizes for some experiments I have to run. Lehr's rule states that we need: $$ n = \frac{ 2\left(z(1-\alpha) + z(1-\beta)\right)^2 \sigma^2}...
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Reviewer wants "post-hoc" power analysis for a mixed effect model [closed]

I have a multilevel model in a mixed design: mod <- lmer(score ~ group*time + (1|id), data = df, REML = FALSE) Where score is continuous variable, group is a ...
Imhotep's user avatar
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What does it mean to run a power analysis for one variable in a multiple logistic regression?

I'm analysing a published logistic regression with 11 predictors, $\textrm{logit}(Y) = \sum \beta_i X_i$. The study unfortunately only reports which of the $X_i$ are significant predictors, and does ...
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Estimate random effect variance for power analysis in multilevel model

Is there a general convention on what variance to expect for a random intercept in a multilevel model? I need to provide an estimate for the power analysis. It is a within-subjects design. Thanks!
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What is the interpretation of alpha and beta within the plots of a H0 and H1?

Reading about statistical power they draw this: and say: Illustration of the power and the significance level of a statistical test, given the null hypothesis (sampling distribution 1) and the ...
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Power analysis for ANCOVA

I'm interested in conducting power analysis for experiment design and inference using ANCOVA. I see questions A,B,C vary in terms of quality, applicably and answers; whereas I'm interested in an ...
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Effect size/power analysis of categorical variable in multilevel model

How to decide the effect size of a categorical variable with multiple levels (e.g., three or four) in MLM? And how to calculate the power of such variables using a simulation (or other) approach?
Misaya's user avatar
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Multinomial logistic regression sample size

I'm an undergrad student completing my dissertation research proposal. I am trying to calculate a sample size for my multinomial logistic regression analysis. The criterion variable is degree type ...
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Interpreting the result of post hoc power calculation with powerCT.default for proportinal hazards model

I have 2 samples of data both with over 800000 instances. . In both samples, ~ 75% of people have the exposure. In the first sample 0.3 % of people have an outcome and in the second 5% have an outcome....
Milo's user avatar
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2 answers
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F test to compare variances. How is ncp calculated to obtain the F distribution under the alt hypothesis?

Recently I needed to do a power analysis for a comparison of variance with a F test. In the past I used the OC curves from Edwin Crow's "Statistics Manual" Chart VIII to get beta. https://...
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1 answer
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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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Power of Test in a Coin Toss Experiment

I am trying to understand the concept of "Power of Test" using the example of a coin experiment. I have a coin that I want to prove is biased towards heads. I toss the coin 10 times, and get ...
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How to measure standard deviation for a power test

I have a "so dumb I'm embarrassed" question about calculating power. Suppose a paper tells me, in "Table 1", that the standard deviation of $y$ is 0.8. And then it reports an ...
dash2's user avatar
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Asymptotic Distribution and Describe Sources of Increasing Power in an hypothesis testing problem

I am currently dealing with the following problem in a past exam (with no solution): Suppose $S$ follows the Poisson distribution with mean $2\lambda>0$, here $\lambda$ is a parameter. Another two ...
INvisibLE's user avatar
1 vote
1 answer
79 views

Power Analysis for Multiple Treatments per Respondent in Survey Experiment

I am running a vignette survey experiment with 6 total treatment options (5 treatments, 1 control), where each respondent randomly receives 2 of the treatment options and answers the same set of ...
flâneur's user avatar
1 vote
2 answers
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Mixed model: Which parameters to provide for sample size calculations?

I am currently planning an analysis in a relatively new area of research and would like to provide data that will allow for future power analyses. Unfortunately, I am completely lost in the ...
a.henrietty's user avatar
4 votes
1 answer
123 views

Sample size calculation for proportional odds model

Apologies in advance for my lack of statistical knowledge/insight! I am trying to calculate the sample size for a clinical trial of treatment A versus placebo with primary outcome of prolongation of ...
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Sample size calculation within-subject

I need to conduct a sample size analysis for an experiment with the following characteristics: One intra-subject independent variable is the type of cheese with two levels, Cheese A (1) and Cheese B (...
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Calculating Sample Size for Cumulative Link Mixed Model (CLMM)

I am going to collect data in which each participant answers to 3 questions to 18 vignettes (each vignette has 3 questions), each question with likert scales 1-5. The dependent variables (questions) ...
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Simulating Power Analysis for Mixed Models (lme4 and simr)

I would like to calculate an a-priori power analysis for a within-groups study with the following design: participant_id condition (within groups - A, B) covariate (scale 1-7) questionnaire items (...
becbot's user avatar
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2 answers
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Is the post-hoc observed effect size redundant with the p-value, just like post-hoc observed power is?

Assume for simplicity sake that we are running a 2-sample t-test on 2 normally distributed populations, from which we collect 2 i.i.d samples. (for a start; we can expand later to more complex cases). ...
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Why does higher variance between clusters increase the power to detect the effect in Poisson mixed GLM?

I simulated the dataset below and I am trying to fit the Poisson GLMM with random intercepts and calculate the power to detect the effect of $x$. When I increase the variance between the clusters ($0....
treskov's user avatar
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1 answer
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How do I calculate the power and effect size for the Wald-type statistic of the RM-function from the MANOVA.RM package in R?

I have calculated the RM-function from the MANOVA.RM package in R and now need to calculate the statistical power of the test and the effect size for its Wald-type-statistic, including the ...
Luise's user avatar
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Sample size calculation for generalized linear mixed models - variance assumption for the random effect

Introduction I would like to perform a sample size calculation for the Poisson generalized linear mixed model. I will leave out irrelevant details, I need to deal with clustered data and the model has ...
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Required sample size for logistic regression?

Early stage PhD candidate trying to suss out project specifics. Currently trying to calculate the sample size required for a binomial logistic regression with one IV and one DV, alpha level 0.05 and ...
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Regression model detects effects that are much smaller than it was powered to detect

I have a mixed-effects regression model with n=250 in each condition. My power analysis predicted that the model would be able to detect effects larger than Cohen's D = 0.20. However, the model ...
Benji's user avatar
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3 votes
2 answers
113 views

Statistical Thresholds for RNA-Seq Analysis: Considering the Intersection of Treatment Effects

I'm conducting an RNA-seq experiment involving worms exposed to chemicals A, B, and A+B to observe mRNA changes due to exposure. I'm particularly interested in identifying mRNA changes in the A+B ...
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Predict benefit of gathering additional data

I have generated data upon which I then perform thousands of independent tests and look for which are significant at a p-value threshold of 0.01 after multiple hypothesis correction. This gives useful ...
John's user avatar
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1 answer
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General Lower Bound of Power in Neyman-Pearson

Let $X$ be an $\sigma$-finite space $(\mathcal{X}, F_{\mathcal{X}}, \nu)$ valued absolutely continuous random variable whose distribution is one of $P_0 = f_0(x)d\nu(x)$ or $P_1 = f_1(x)d\nu(x)$. We ...
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Regression with depended predictors, animal study sample size [closed]

I have a few questions for help, One of my predictors is for treatment and control. Another predictor is dosage. Treatment group has 4 dose levels which control group only has one. Can I still use ...
aqen's user avatar
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11 votes
4 answers
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Is it possible to calculate the power for a specific beta coefficient in a multiple linear regression?

I want to conduct a multiple linear regression where I am only interested in interpreting one beta coefficient but I will adjust for two additional covariates (i.e. three variables total). Is it ...
Tom's user avatar
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1 answer
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Small sample in categorical explanatory variable vs overall sample size

In a statistical model e.g. regression, we have to ensure the sample size is sufficient to estimate a given number of parameters. Rules of thumb e.g. n=10 per parameter, or a power analysis, will ...
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