# 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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### power and sample size estimation

For a one-sided test: $$H_0: \mu_1 \leq \mu_2 \ H_1: \mu_1 >\mu2$$ $$\alpha=0.025,\beta=0.1$$ How to calculate the sample size needed? Is this information enough to calculate the sample size?
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### P-value under 5% but power under 80%

Im trying to understand how to accurately report results on AB tests If my type 1 error is 5% and type 2 is 20% , can we have instances where the p-value is < 0.05 and power is < 0.8? If so, how ...
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### Calculate sample size for multiple treatments vs control, given the proportion mix of treatments

I want to know what my sample sizes should be for each of my treatments and control, given a proportion mix between the groups. For example, let’s say I have 3 treatments (A, B, C) and 1 control (D). ...
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### Sample size calculation for Cox regression with time-varying exposures

I'm involved in the design of a longitudinal observational study investigating a relationship between the use of a drug and a binary outcome. Participants are enrolled when at risk of the outcome, ...
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### Power / sample size estimation for chi-square test with continuity correction in R

1._Some authors mention that they estimate sample size for chi-square test with continuity correction. For instance: Sample-size calculation is based on Pearson's Chi-square test with a two-sided ...
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### How to deal with ragged power curve

I am exploring various methods for sample size calculation and power analysis from binomial data, and frequently coming up against ragged power curves that go up and down as sample size increases. I ...
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### Questions for calculation power/sample size in (multi group) structural equation modeling

I will measure a certain characteristic in an intervention group and in a control group over four points in time. I want to construct a latent change score model to check if the groups develop ...
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### Report power if result is statistically significant

We have submitted a paper reporting a statistically significant result. One reviewer asks us to report what is the power to detect a significant association. As there was a previous paper on this ...
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### Error in wp.logistic: ‘p0’ must be numeric in (0,1)? What to do when p0 is negative?

I am trying to find out the sample size I need for a future study using a reanalysed existing dataset to enter the values in a WebPower script. I am using the intercept and odds ratio/estimate of my ...
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### Power with a hierarchical multiple regression analysis [duplicate]

I was wondering how to calculate the power with the below data? I did a hierarchical multiple regression with two models. There are a total of 87 participants and the alpha level is 0.05.
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### How to calculate your power in GPower? [duplicate]

I was wondering how you calculated the power via Gpower with these results? There are a total of 87 participants and the alpha level is 0.05.
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### How to calculate power?

I was wondering how you calculated the power via Gpower with these results? There are a total of 87 participants and the alpha level is 0.05. It is a longitudinal design in which I performed a ...
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### Post hoc power analysis for multilevel regression analysis

I have a multilevel model with 2 levels (L1 = individuals, at least 710 per country; L2 = countries, 17 total) ...
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### How to Ensure Saturation Using Grounded Theory?

In quantitative causal inference, we do power analysis to determine the minimum sample size to achieve (1 - $\beta$) statistical power of our hypothesis test with a specific $\alpha$ statistical ...
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### When the anticipated sample size is not reached in a clinical trial

How to justify precisely a situation where the expected sample size is not reached? For example, the sample size for our study protocol was determined on the basis of a fixed statistical power of 80%. ...
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### repeated measures design vs. MANOVA power analysis

My collaborator and I are building a study where participants will read some profiles that vary for 3 dimensions each having 3 levels (9 profiles in total). For each profile participants will have to ...
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### Power issue for categorical vs. continuous predictor in lmer

I have the following model: ...
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### Does StatsModels' power.tt_ind_solve_power assume a single standard deviation despite two different means?

Does StatsModels' power.tt_ind_solve_power (link) assume a single standard deviation despite two different means? I think so. Why is this a reasonable assumption? I come from a primarily Bayesian ...
1 vote
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### Question regarding post-hoc power analysis

I am having trouble with interpretation of a prospective superiority randomised controlled trial. Study characteristics: Study design: Alpha value = 0.05 1-beta = 0.8 Predicted effect size =0.15 [P1 =...
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### Required sample size of CFA using power analysis from semPower

I want to conduct a confirmatory factor analysis (CFA) for a model with 4 latent variables and 60 indicator variables (15 per factor, uncorrelated factors, hence 1,710 degrees of freedom, that is, ...
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### Python package for this power analysis calculator [closed]

I would like to use the following power analysis formula into a python notebook https://clincalc.com/stats/samplesize.aspx Any idea which python package would replicate the same results ? Edit: I ...
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### Convergence algorithm for power analysis?

I found this algorithm on a shared drive and I'm really curious how it works. From appearances, it's used to estimate the MDE in power analysis when the effect size (difference of proportion means) ...
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### Calculating Sample size of a linear regression

I just would like if anyone knows how to calculate the sample size for the data set given the significance level is set at alpha = 0.05 and the power of the test should be 80%. The linear regression ...
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### GLMM: X=Non integer warnings for power estimation

For starters I am both new to R and out of practice for statistics. I am going to run an experiment where participants answer a survey every day for a week, and I want to figure out the sample size I ...
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### power analysis via Monte Carlo when effect size, means, and std unknown

Say you want to execute an experiment to see whether a treatment is better than a control and want to properly power your experiment. However, you have no beliefs a prior regarding the treatment's ...
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### Calculating the power of an experiment

I'm working through a question in Gelman - Regression and Other Stories and I find myself getting confused with the following question; 'Power, type M error, and type S error: Consider the experiment ...
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### Most powerful test for hypothesis testing with uniform and exponential distributions

Given sample of single observation $x_{}$, we are checking hypothesis $H_0 \sim U[0, 1]$ versus $H_1 \sim Exp(1)$. I need to find most powerful test for hypothesis checking with given Type I error ...
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### low sample size experimental design, t-test vs one way ANOVA

I'm designing a biological experiment wherein the sample size is very limited, as each sample is very hard to get. Moreover, I need to have 4 independent groups, each receiving a different treatment. ...
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### Power estimation and analysis for multiple 3x3 count tables

In my design, each subject produces a 3x3 contingency table.So I have a table of counts of how many times a subject responded X Y Z in condition A, B or C. All the columns sum up to 50 (num of trials ...
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### How to calculate how many levels of nuisance factor I need for a desired power level in my experiment

I have a nuisance factor that introduces a lot of variation in my data. I want to know how many levels of this factor I need to include in my blocked design to get a power level of, say, 90%. As an ...
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### Compare mean of subsamples between groups

I am going to collect quantitative data for two groups that I would like to compare. I have done a two sample t-test on some preliminary data and found a significant difference, but I don't think that ...
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### Computing the power for binomial regression with indicator variables

My question is kind of a sequel to this one. For an experiment I'm designing, I want to model the outcomes by a binomial regression, something like ...
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### What is the purpose of accrual period in survival analysis?

Before reading the answer to this question, I, like the original poster, thought that we have to take the accrual period into account because some subjects might die before we start the treatment. But,...
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### Mixed Model Convergence Issues With LMER

I am fairly new to statistics and I want to run power analyses on my models, so I was hoping to get some insight on model convergence issues. I am using a dataset in which I am examining the effects ...
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### Three-way manova or separate anovas?

I have three independent catagorial variables and two dependent continuous scale variables, so I want to compare means across these three independent catagorial variables. I think here the best choice ...
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### Power analysis: How do you calculate the power (1-B) based on the matched-pairs biserial correlation effect size?

I am running a Wilcoxon-signed rank test, and as suggested by King et al., the best effect size to report for this analysis would be the matched-pairs rank biserial correlation. How is the power (1-B) ...
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### How to power a strong superiority hypothesis in an A/B test

Suppose I would like to perform an A/B Test, where it only makes sense to implement the "treatment" over the "control" if the "treatment" is atleast 2% better than the &...
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### Is it incorrect to say that $\text{Power} = P(\text{reject } H_0)$?

Is it incorrect to say that $\text{Power} = P(\text{reject} H_0)$? I've seen in my textbook as well as other sources power is always defined as the conditional probability \$P(\text{reject } H_0 : H_a ...
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### Statistical power of tests on unequal and known variances vs equal but unknown variances

Suppose you are testing for differences in two normally distributed variables. In the following situations: -Variables have known but unequal variances -Variables have variances that are unknown but ...
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### How to get within standard deviation in mixed models

I wonder how to get the within standard deviation in mixed models. Does anyone have an explanation? If not in mixed models, how would it otherwise be done? Thanks! ...
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### What is the different between t(3) and Ca(0,1) distributions

I did a simulation study for empirical power for normality tests Shapiro-Wilk test and Anderson-Darling test against alternative t(3) and Cauchy distribution with parameters 0 and 1, I know both are ...
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### Is there any reference justificating a P<0.10 as a cutoff for likelihood-ratio tests?

I am conducting log-likelihood-ratio tests to examine the goodness of fit of two competing logistic regression models. The test is the traditional log-likelihood-ratio test, in which I compare the ...
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### Baffling results in the simulation of a power analysis of a sequential, online A/B experiment

I conducted a simulation that had baffling results and would love your help understanding. Context: I want to estimate the required sample size to detect a difference in proportions for a sequential, ...
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### Why do we need statistical power? Why are p-values not enough?

I am looking to understand the need and intuition for statistical power. I understand how to calculate it, but I cannot understand why we need it. Here is my current thinking: Suppose we have a ...
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### How to perform statistical power analysis for generalized linear models on IBM's SPSS?

I ran a generalized linear model (Poisson distribution) on some data of mine. This is my simplified syntax: ...
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### How to do power calculations for secondary analysis?

I am conducting a secondary analysis on a study with 3k participants. My analysis is stratifying the data to look at another outcome of interest. One of my editors has told me to conduct a power ...
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### How do I asses the power of a chi-squared test of independance?

Let's suppose I have two treatments, A and B, that I use on randomly sampled individuals of a population. I want to assess the relation between the treatment and the probability of an event happening ...
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### Is it better to have many measurements each with few data points or few measurements each with many data points?

I've wondered this for a long time. Let's say that I'm designing an experiment e.g. to measure human reaction time to images in which the contrast is varied. If I can afford 1000 trials I could make ...