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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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What is the variance of the standardized mean difference of two independent studies?

I have computed the standardized mean differences for a pair of independent samples. But when I Googled for the "variance of the standardized mean difference" I got rather confusing results, with ...
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correlation-based effect size

how can a correlation coefficient of .40 be a "medium" effect size when r2 shows that the variables only have 16% common variance? Seems like the 16% suggests a small effect size. Jim
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Can the r-scale value (for Bayes Factor) be directly based on Cohen's d?

I want to set an r-scale value for a Bayesian t-test (i.e. to calculate Bayes Factor likelihood ratio) based on previous results (i.e., from a posterior). But I simply cannot find a straightforward ...
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How to interpret a statistically signficant finding that becomes unsignificant after bonferroni correlation

I hypothesised I would find a main effect of X which I did (p=0.028), however, upon using the bonferroni correction my alpha dropped to 0.0125, making this result no longer significant. I found a ...
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How can I calculate confidence intervals for epsilon-squared (Effect size for Kruskal-Wallis test) in R? [closed]

I'd like to calculate the confidence intervals for the epsilon-squared effect size statistic in R. Here is the code I'm using to calculate the epsilon-squared value: ...
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Choosing the measure of effect size to extract&summarise in a meta-analysis

I am preparing a meta-analysis for a certain therapeutic intervention, and will be interested to quantify/summarise the change in various scores, pre-to-post intervention. Which measure of effect ...
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Applying Cliff's delta to paired data

Wikipedia provides a few ways of calculating Cliff's delta - an effect size quantifying distributional shift. However it only talks about having 2 samples that are unpaired. While one can apply the ...
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Effect size for One-sample Wilcoxon Signed-rank Test

I want to use One-sample Wilcoxon test.However, I do not know how measure the effect size. Any test suggestions?
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Converting between correlation and effect size (Cohen's d)

Several sources (here here here) claim that there is a relation between Cohen's d and Pearson's r if the data is paired (bivariate). This strikes me as odd since, for example, evaluating a "before and ...
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Obtaining measures of effect for contingency tables with multiply imputed data

The epi.2by2 function in the epiR package computes a chi-square test and provides measures of effect when count data are ...
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Are effect sizes calculated for prospective/ retrospective cohort studies that look at odds ratios?

Are effect sizes calculated for prospective/ retrospective cohort studies that look at odds ratios? I apologise if this is a silly question
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Reporting effect aize

Could someone please explain the difference between standard mean difference and adjusted mean difference. I want a common rubric for reporting effect size.
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Interpretation of partial eta-squared in factorial designs

I'm having troubles interpreting and comparing effect sizes in factorial designs based on partial eta squared values. E.g. in a 3x3-within-subjects design with: η²part, A = .2 η²part, B = .4 η²part, ...
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1answer
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How to determine sample size for Chi-squared test?

Similar questions have been asked here on CV, however I have not found a solution to my specific question yet. I am trying to plan a sample size for chi-squared test. However, I struggle to find the ...
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How to calculate the effect size for a t-test?

The pwr package includes the function pwr.t.test, which relates the following four quantities: sample size effect size ...
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1answer
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How do I get a measure of effect size for each term in a multilevel model?

For a multilevel model of the form, say: $$Y_{ij} = B_0 + B_1X_{1_{ij}} + B_2(X_1)^2_{ij} + B_3X_{3_{ij}} + B_4X_{1_{ij}}X_{3_{ij}} + B_5X_{5_j} + (u_0 + u_{1_j} + e_{0_{ij}} + e_{1_{ij}})$$ Does ...
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Magnitude of the effects using confidence interval [closed]

I have an assignment (doing regression) and one of the tasks is "Check the magnitude of the effects using confidence intervals.". How can I check this and how to report it in a paper? Using SPSS.
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why is the effect size in sjstats anova_stats NA

I am trying to find the effect size of my mixed effects model. I found sjstats provides several outputs including eta-sq, ...
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How am I able to compute the effect size and variance for the given data?

I am currently studying a research paper in which the following data is given: Control group prevalence estimate: 5.1% (standard error = 1.9), n=138 Treatment group prevalence estimate: 13.0% (...
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Is there a commonly accepted effect size parameter for pairs of Bernoulli processes?

Let $f(x|\rho)$ be the Bernoulli pmf with probability $\rho$ of success. \begin{align} f(x|\rho) = \left\{ \begin{array}{ll} \rho & x = 1 \\ 1-\rho & x=0 \end{array} \right....
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Is it possible to determine significance with a defined alpha (.05) from an effect size estimate with a 95% CI?

Say for example, there is an observed estimated standardized mean difference of $d = 0.44$ with $CI_{95} = [-.10, .89]$. This is the only information we have available (i.e. we do not know the sample ...
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Calculate correlation from paired t test's results

I have the degrees of freedom, difference between means, 95% confidence interval, and p-value of a paired t-test (i.e., a t-test run to analyze pre-post scores). I need to calculate the corresponding ...
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Multiple Regression Effect Size, Significance, and Cohens f^2

I have a multiple regression with a continuous dependent variable, 1 continuous independent variable, and a handful of binary independent variables. The R summary is pasted below: ...
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1answer
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Which effect size when sample size and variance are not equal

I don't have extensive knowledge in statistics, therefore I have some trouble to understand which metrics I should use for my analysis. I have measure a feature (concentration) of multiple substances ...
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The curious case of the mysterious repeated measures effect size estimate

I am currently in the middle of a stone-cold statisical whodunnit. I need to find the name of an effect size statistic a recently departed colleague used for a project, measuring effect size of change ...
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1answer
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Relation between t-value and correlation coefficient r

Page 6 of this article shows that following holds for an "independent samples t-test". I was wondering how the equation to the Right of equal sign would change if we consider a "paired samples t-...
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1answer
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Meta-analysis with response ratio effect size

I am interested in comparing the performance of two different techniques (i.e., Method A vs. Method B) on a continuous outcome of interest. The performance of such techniques is measured through test ...
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Non-parametric equivalent to Z-factor?

It seems that all the ways of calculating standardized effect sizes assume a normal distribution: Z-factor, Cohen's d, SSMD, ... I wonder if there is a non-parametric equivalent to these. In ...
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Converting Cohen's d to r for two paired groups

I know that there is an exact formula for converting a Cohen's d effect size to a Pearson correlation coefficient ($r$) in the context of two 'independent' groups as discussed HERE (see p. 6): $r = ...
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Calculating effect size for EEG data

Our data is from two scalp EEG channels (C3 and C4), which correspond to the sensorimotor cortex on each side of the brain. We are looking at how effect size of a waveform metric differs between ...
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1answer
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What is the standard error of the difference in means scaled as percent difference?

Biologists frequently report the effect B-A as a percent difference (or relative effect), for example "Y was 25% bigger in treatment B than treatment A", where 25% = 100*(B-A)/A and A and B are the ...
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How to compute effect sizes of single predictor in a logistical regression?

I have a logistic regression, with a binary response, a continuous predictor, and a categorical one. Is there any way to calculate the effect size of each of those predictors, similar to partial eta-...
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How do I estimate Glass' ∆ confidence interval?

In looking for a guidance on calculating confidence intervals for Glass' ∆ effect size estimator. There are plenty of online content and answers here on how to calculate the confidence interval for ...
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1answer
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Calculating effect sizes when a certain proportion of subjects give one of four answers

How can an effect size be calculated between two groups when the data is reported in frequency proportions (e.g., each group has people who have answered a question about relationships with either: ...
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“effect size is independent of sample size” really?

I keep reading "effect size is independent of sample size" on the interwebs. Don't get me wrong, I get the practical vs statistical significance considerations. What I don't get is that; -power,...
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Are effect sizes on different populations comparable?

Does it make sense to conclude that an effect is (likely) stronger in population A than in population B because the effect size estimated on A is larger than that estimated on B? (The samples are not ...
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Comparing non-independent metaanalytic effect sizes

I am running a random-effects meta-analysis on a collection of placebo controlled trials. Each trial reports on the effects of the drug and placebo on 'positive symptoms' and 'negative symptoms'. I ...
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1answer
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Regarding difference between paired and independent effect size

I calculated the two standardized effect sizes (i.e., once for paired samples and once for independent samples) and got two different values (0.45 and 2.58). Why are they different?
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Log-transformed DV and coefficient of interaction term

I am having difficulty interpreting the significance of positive tone (measured as percentage of words in a sentence that are positive in tone) for females and males. The following is the regression ...
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1answer
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Why are effect size estimates difficult in mixed-effects models?

I have been reading a lot online about estimating standardised effect sizes in mixed effects models and it seems like there are formidable challenges even for something relatively broad like an R^2, ...
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Classical Cohen's d effect sizes within mixed-effects models

I am trying to get a passable effect size estimate of group differences in slope from a trend analysis, run by specifying custom polynomial contrasts within a factorial mixed-effects model. This blog-...
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Compute Becker's (1988) standardized mean change based only on difference score and t-statistic (meta-analysis)

In my meta-analysis, I'm combining independent-sample designs with single-group pretest-posttest designs. To ensure interpretability across designs, I would like to quantify the effects from pretest-...
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1answer
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How do I identify the magnitude of the difference between two moving averages?

I am trying to identify not only when two moving averages diverge, but when they do so by enough for it to be important. With the data I am using (not stock market data), the two averages will cross ...
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How to Bootstrap the Power in a Regression Hypothesis test

I am running a regression $Y=\beta X$ having several covariates, and my hypotheses are: $H_0$: $$\beta_1 = 0$$ $H_a$: $$\beta_1 \neq 0$$ I want to use the bootstrap to compute the power of the test $...
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Detecting significant effects based on critical t value for a given sample size

"Because (this study) collected 77 participants in total, and used an alpha level of .05, the critical t-value is 1.99. This critical t-value can be transformed into a 'critical standardized effect ...
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Meta-analysis - effect size from multiple severity groups

I am currently performing a meta analysis to evaluate whether a measure (let's call it Meas) is correlated to the severity of a disease (Sev). The severity of the disease is reported as a score from 0 ...
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1answer
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Can effect sizes (SES) be compared when the underlying null distributions are different in a meta-analysis?

Background: In community ecology one of the questions we are interested in is if the species in a community are non-randomly associated. To try and get at this we typically use a null modelling ...
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Confidence interval of median difference, SPSS

Despite some great help on here I'm not 100% sure about calculating 95 CIs for median difference. This is my procedure at the moment. I've got a repeated measures design, so behaviour of animals in ...
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Is there a rule of thumb regarding effect size and the two sample KS test?

I have performed the KS test comparing two samples. My sample size is very large so the p value is very low even though the effect looks weak. I found a an explanation for the calculation of the ...
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Reporting the effect size for Welch's ANOVA

I ran a Welch's ANOVA test with Alpha= 0.05 between 3 groups od data (n=7 for each) followed by a Games Howell test. The Welch's test is not significant (p-value=0.104). I believe I need to report the ...