# Questions tagged [effect-size]

Effect size is "a measure of the strength of a phenomenon or a sample-based estimate of that quantity" [Wikipedia].

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### Linear mixed model: How do z-standardized coefficients relate to effect size?

I have a very simple linear mixed model: Y ~ condition * rating + (1|subject). Condition is a factor with 3 levels and coded using treatment contrasts. Hence, I compare level 1 and level 2 with level ...
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### What is the effect size h in pwr::pwr.p.test in R?

The R package pwr has a function for calculating the required sample size for a one-sample proportion test (I assume a z-test ...
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1 vote
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### Can a consensus be reached on the exact meaning of "Cohen's D" and "Hedge's G"?

This question: Difference between Cohen's d and Hedges' g for effect size metrics shows there are at least two different interpretations each of both Cohen’s D and Hedge’s G, one of them in ...
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### How to calculate effect size for impact measurement in a quasi-experimental study? [closed]

I have baseline and endline mean scores and standard deviations, respectively, for a treatment group and comparison group (4 sets of data each for control and treatment). I need to calculate the Cohen'...
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### Determining direction of effect in Wilcoxon Test and interpreting pseudomedian in R

I originally posted this on Stack Overflow (https://stackoverflow.com/questions/72649894/determining-direction-of-effect-in-wilcox-test-and-interpreting-pseudomedian), but I realized it fits better ...
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### Design of Experiment, sample size and repitition

When designing resp. performing an experiment, I'd come up with something like this finally: A question of such an experiment is whether to include repetitions, where you'd simply repeat the entire ...
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### Meta-analysis in R: multiple effect sizes with unknown correlation

I'm working on a meta-analysis with multiple effect sizes reported in most studies. My effect sizes are SMD between two groups (health/ disease) and the reason there is multiple effect sizes per study ...
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### Detecting statistically significant change between multinomial samples and individual category proportions

Say I have a categorical variable with more than two categories, e.g., a person's country of origin. Assume the number of categories is some finite $k$ (e.g., not dealing with distribution of people'...
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### Why I can recover the total effect with OLS but not with logistic regression?

The dataset ISLR2::Default contains one observation per individual. The variable Default is "Yes" if the individual ...
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### Effect size and statistical significance correspondence

While I understand that it is possible to have a small effect size with statistical significance and a large effect size without statistical significance, is it ever possible to find this across two ...
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### Building a bootstrapped distribution to test reliability of empirical data

I have data from a study where subjects (considered as "generations" in a Telephone-like game) sang short melodies from one to the next, starting from a randomly-generated melody (seed) ...
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### Calculating global and local effects in a multiple regression using Cohen's d

I am calculating the effect size Cohen's d using linear regression. I am looking at the effect of disease on memory, and have also added age, education and sex as confounds to the regression. Cohen's ...
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### lmer anova effect sizes

I would like to compute the marginal R squared for the whole factors from an anova table. This post shows how to get the effect size for each fixed effect based on the ...
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### Meta-analysis with ratio data

I am currently performing a meta-analysis where the outcome of interest is the ratio between the concentration of two sugars in urine/plasma (i.e. the results of dual-sugar test; see: https://doi.org/...
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### Effect size calculation on a MANOVA with contrasts

I would like to conduct a repeated samples (patient) ANOVA (with Factor X with 3 levels A, B, C) with the planned contrasts (A+B)-C (i.e 1 1 -2) and (A+C)-B (i.e 1 -2 1) as well as calculate the ...
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### How are effect sizes calculated following a cellwise residual analysis?

I have used SPSS to create a 2X4 contingency table concerning the relationship between two categorical variables: depression diagnosis and 4 sleep disruptions. I carried out a chi square test of ...
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### Spearman's Correlation and effect size

I have completed data collection and I have a Spearman's correlation of .64. My advisor is wanting me to report the effect size and from everything I have read and can find it appears that .64 would ...
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### How should I calculate effect sizes for a 2X4 table?

I have used the software SPSS to produce a 2X4 contingency table, using categorical data. I am aware that odds ratio is only applicable for 2X2 tables. Are there alternatives to odds ratio to try and ...
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### Intuitive effect size (and CI) for one-way comparison of group means?

I'm a big fan of common language effect sizes (e.g. McGraw and Wong's CL or Cohen's U3 - "what proportion of group 1 are higher than the average for group 2"). I've been scrabbling around ...
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### Effect size: difference between Cohen's d and Wilcoxon's r?

In the simple case where I have N trials with mean result $\mu$ and I want a measure of how on the whole they differ from a theoretical model of a normal distribution with mean 0 and standard ...
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### Cohens d in relation to a single case

Cohen's d in relation to a single case The average effect size (Cohens d) for insomnia-treatments ranges from about 0.3 to 0.4. If I had a patient that suffered from insomnia 4 out of 5 weekdays (...
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### How was effect size calculated in this study?

I am trying to learn about effect sizes and how it relates to real-world data so I looked at a random study for insomnia-treatment: https://onlinelibrary.wiley.com/doi/10.1111/jsr.12067 and the ...
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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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### In a 1-way ANOVA, is the square-root of the coefficient of determination the intra-class correlation?

The actual question I mean to ask is if the square-root of the effect size is the intra-class correlation (ICC). When the 1-way ANOVA test is viewed as a bivariate analysis between a categorical ...
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### Conflict Between Confidence Interval and P-values - One Sample T-Tests

I'm conducting one-sample t-test using R. I calculated p value, effect size, and confidence interval, but they seem to be conflicting. Here is a sample code and output: ...
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### Effect size calculation?

We are currently analyzing medical records data. During the study period, we have a minimum of 60,000 population patients in group ...
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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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### Small/Medium/Large Cramér's V effect size tables available for degrees of freedom > 5?

I've come across numerous tables published online categorizing Cramér's V effect sizes for categorical tables with degrees of freedom $\leq$ 5, for example:  \begin{array}{c|lcr} \text{Degrees of ...
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### Transformation eta sqaured into cohens d or r

Is there a possibility to convert eta squared to Cohen's d or r? I uded this page (especially calculator 14) to transform different effect sizes into one: https://www.psychometrica.de/effektstaerke....
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### Integrate chi-square-tests in meta-analysis

I would like to do a meta-analysis, based on community-based intervention studies. In the studies the chi-squares and the p-values are given. But the sample size is related to entire cities, so I don'...
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### Adjusting effect sizes, p values, and CIs for sequential analysis via simulation

It's fairly easy to write a simulation procedure to calculate, for any given global type 1 error rate, adjusted local "stopping" alphas for interim "looks" in a sequential design, ...
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### effect size for pairwise permutation

I am reading a paper that is using permutations to compare the means of two different treatment groups (a nutrition study, took minimum - maximum) that have low sample sizes, and so the groups are ...
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### Effect size measure for post-hoc tests after nonparametric tests: Alternatives to calculating r from z score?

I've calculated Friedman's tests for my data and want to report an effect size with the individual post-hoc tests that followed on from the statistically significant Friedman's test. I use the formula ...
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### common effect sizes in psychological research and calculation/ transformation

I am working on an empirical literature analysis. For that I have to code some variables in a specific manner (analysis includes 150 published studies in the field of behavior Neuroscience, ...
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### Sample size calculation for a three arm clinical trial study

I have a 3 arm clinical study with two drugs and placebo on the three arms respectively. I intend to perform a Log-rank test on it. I would like to know about the best software which is globally ...
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### Extracting repeated measures standardised difference from studies for meta-analyses (unknown correlation between measures)

I am conducting a meta-analysis and trying to extract standardised differences from a study using pre-post (or repeated measures) design. I am given the Mean, SD, and Sample Size for the pre- and post-...
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### Effect size - is correction for multiple comparison needed?

I have a general question on whether effect sizes need to be corrected for multiple comparisons. I need to conduct 8 t-tests, in order to test whether values from 8 different conditions different ...
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### Calculate power-effect size relationship for difference in difference of proportions

I am trying to conduct power calculations for a "Before-After-Control-Impact" type of study focused on public opinion variables. Ideally, I want to look at the relationship between effect ...
1 vote
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### Using Cohen's f squared to calculate effect size between rank-based correlation coefficients

Is it reasonable to use a Cohen's f squared to calculate an effect size between two Spearman's correlation coefficients that are squared and equivalent to R squared? The idea is that this comparison ...
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### Should I use effect sizes from multiple regression or raw correlations for meta-analyses?

I am conducting a meta-analysis and have encountered a study that provides both correlation coefficient and multiple regression statistics for the same effect. Is using effect sizes from multiple ...
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### Arcsine transformation for two sample proportion test

I'm planning a two sample proportion test and was asked to calculate what sample size is needed to show a certain effect size at a give level of power and significance. The book I'm using (Statistical ...
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### Correlation coefficients when oversampling the extremes of a normal distribution

Running some simulations in which I generated two correlated normal variables (rho=0.3), and then took samples of this population in which the extremes of the population where oversampled (...
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