# Tagged Questions

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

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### Election result: How to test for significance?

I guess this is a very basic question, but I find myself unable to find an answer. I have asked a sample of probands (N = 467) which one of three presidential candidates they would elect, A, B, or C. ...
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### Multiple regression analysis with 22 data points and 7 independent variables [on hold]

I am working on my thesis and want to do do a regression analysis to find the effect per 'problematic factor' (see attachment) on 'Duration' (see attachment) or 'Costs' (see attachment). Chance here ...
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### Calculating Standardized Response Mean

I was told that standardized response mean was calculated as "absolute mean change divided by the standard deviation of individualsâ€™ change in score." But, other websites say "the difference between ...
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### Equivalence of paired-samples t-test and repeated measures ANOVA with two conditions regarding effect size estimates

To compare two within-participants conditions, I ran two tests (with SPSS): A repeated measures ANOVA with one factor with two conditions and a paired-samples t-test. I thought that these two tests ...
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### Estimating effect size for mean difference (Cohen's d) in a structural equation model

I would like to ask for you help in the following matter. There is a structural equation model (SEM), which in one of its regression parts estimates the effect of gender and a few other factors on a ...
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### Interpreting an interaction effect plot and effect sizes range

I have two questions please. One, how can I interpret the following plot where there is an interaction between a categorical variable of four levels (context) and a continuous variable, frequency? ...
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### Percentage increase for Treatment/Control in a cohort education study

I have some Baseline and Midline results in a treatment/control study. In trying to calculate effect size for the treatment group, I'm using a Cohen's d calculation which allows for the discount in ...
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### Weighting average similarity/correlation values by number of correlations?

I have a dataset containing correlations and other similarity measures between musical performances of which the performer and his nationality etc are known. Now i want to analyse that dataset; ...
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### How do I calculate the probability of getting a particular effect size given multiple comparisons and no true association?

I have a hypothetical research scenario involving multiple comparisons and I want to try and prove my hunch right or wrong! Following a medical intervention, scores for 12 outcome measures are taken ...
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### Confidence interval for effect size for a within-subjects t-test

does anyone have a suggestion for an expedient way to calculate confidence intervals on effect sizes (cohen's D) for dependent-samples (edit: within-subjects) t-tests? For a meta-analysis, I've ...
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### Effect size for comparison of two nested models

I want to calculate an effect size for the difference of two structural equation models (model 1 and 2). Model 2 is nested in model 1. For each model I get a $\chi^2$ as measure of fit. Whether the ...
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### The value of an Effect Size

I calculated a Cohen's d value of d= -2.1. I understand that there are small, medium, and large effect sizes. But in my case the d value is negative? Would it still be considered large since abs(-2.1)...
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### Which of the several measures of d-statistics is better for a meta-analysis of effect-sizes?

Several measures including Cohen's d are available for computing d-statistics. It is difficult to choose one of them for a meta-analysis? Are there any guidelines ?
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### Help with choosing the correct effect size

I conducted a two-way between groups ANOVA to test the impact of video gaming (gamer/non-gamer) and gender (male/female) on reaction time. I'm conducted my analysis using SPSS and received the ...
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### Interpreting partial eta squared [duplicate]

What are the values for small, medium, and large partial eta squared? Is partial eta squared $\eta$ or $\eta^2$?
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### Calculating sample size for two-way ANOVA given effect size

I have an experiment with two groups and three timepoints (different subjects for each timepoint, so no repeated measures), and I understand a two-way ANOVA would apply to this situation. I'm trying ...
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### Independent measures for pre-post data

In conducting a meta-analysis, I have pre-post data from single case designs. Unfortunately, I do not have access to the correlations between the pre and post scores. Is it correct that if I ...
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### 2X2 ANOVA: low power, statistical significance for only 1 IV, medium-low effect size

BACKGROUND: I run a 2X2 Between-Subjects ANOVA. I obtained: a low power (< 0.30) for both Independent Variables a not statistically significant result for one of the Independent Variables. ...
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### Within subject effect size when no correlation available

I am doing a research project on the topic of replicability in psychology. To do this, I did a set of 10 meta-analysis on different studies. My problem is the following : some of those studies were ...
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### How to interpret rank-biserial correlation coefficients for Wilcoxon test?

I know that Pearson's $r$ correlation coefficient can be classified as follows (Wikipedia entry): small size if $r \in [0.1, 0.3)$, medium size if $r \in [0.3, 0.5)$ large size if $r \in [0.5, 1]$ ...
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### Which effect size analysis is most meaningful for mixed ANOVA

I'm trying to get my head around which effect size is most meaningful for a 2x2 mixed ANOVA for two intervention groups. I have pre and post assessement data (measured at the continuous level) for two ...
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### How to compute effect size for Friedman's test?

I was looking for a way to compute the effect size for Friedman's test, but could not find any reference. I wanted to see if there is any difference between the groups and what its size was. I have ...
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### Compare effect sizes in GLM, in order to do species grouping

In an analysis of mine in ecology, I'm trying to quantify the effect of some crop surface on the abundance of several species. What I'd actually like to do is to see if the effect of crop surface is ...
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### Effect size measure for mxn Fisher Exact Test

I'm using the R function to run fisher exact test for mxn contingency tables (since my sample size <5; limitation of the chi-squared test). Along with the p-value I want to state the effect size. ...
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### Unequal Sample Size Effect on Power Calculation

I am new to power analysis and have been experimenting with one-way fixed effects Anova in G*Power (Fixed effects, omnibus, one-way, Post hoc power). When dealing with unbalanced design, the effect ...
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### Effect size: use standard deviation or standard deviation of the differences?

Consider the effect size for a test between two independent samples. I thought the difference in means compared to the standard deviation, as in this formulas following Cohen but a recent article ...
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### Comparing the effects of variables that have the same nature

I'll try to illustrate my question through an example based on a study I'm carrying out right now, but I think it can be interpreted more generally. I'm interested in assessing the effect of some ...
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### Still confused regarding interpretation of effect size given highly significant p-values

Suppose you have 3 groups, 'Atheists' ($n_1=102$), 'Nones' ($n_2=178$) and 'Religionists' ($n_3 = 390$). You want to find out if there is a difference in the experience of meaningfulness between these ...
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### How to measure treatment effect in Excel pivot tables

I have two pivot tables, one with gallons of gas consumed prior to treatment, and a second with gallons of gas consumed after treatment, which is a mixture added to the full gas tank. See image below. ...
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### Do Cohen's d and Hedges' g apply to the Welch t-test?

How do you go about calculating effect size for the Welch t-test?
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### Approach to conduct meta-analysis including data from structural equation modeling

I'm planning to write a meta-analysis on a topic in which there are both clinical trials and structural equation modeling papers. For clinical trials i can compute easily the effect size and analyze ...
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### Effect size for Wilcoxon Rank Sum test

I'm unsure how to calculate the effect size after applying a Wilcoxon rank-sum test. I'm using scipy.stats.ranksums, where the outputs are ...
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### How to calculate pre and post treatment Hedge's g effect size to use in meta-analysis of studies with no control group?

How to calculate pre and post treatment Hedge's g effect size to use in a meta-analysis for studies with no control group? Can you do it with just pre and post treatment means and standard deviations ...
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### Calculation for the estimated sampling variance of individual group raw mean

I am conducting a meta-analysis where the effect size is the individual group raw mean (i.e., not raw mean difference). A couple of questions: How (in R: metafor or otherwise) is the estimated ...
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### Estimate if effect sizes in a multi level model differ

I have the following model summary: ...
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### What is the way to report effect size for an ordinal logistic regression?

I am very new to working with ordinal logistic regression models and I was wondering what is the best/most appropriate way to report effect sizes for these models. I am using the polr function from ...
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### Using effect size estimates and p-values to determine effect size variance and standard error

I am in the process of conducting a meta-analysis. I am having difficulty replicating effect sizes that are in previous meta-analyses on the same topic. That is, for a given study I am not getting the ...
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### Does Sample Size Affect Partial Eta Squared values when running a Mancova or Ancova?

I am currently running an ANCOVA and MANCOVA for my research and need some help in terms of understanding the Partial Eta Squared(PES) values given to me off on SPSS. I am first wondering if with PES ...
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### Measures of minimal detectable effect size

Statistical power is defined as the probability of wrongly accepting the null hypothesis for a given sample size, p-value cutoff and effect size. I am after accepted measures of the converse: the ...
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### Specifying prior for effect size in meta-analysis

My question concerns priors on effect sizes, in my project the measure is Cohen's D. Through reading the literature, it seems vague priors are often used, such as in the well-know eight schools ...
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### How can I account for range restriction when meta-analytically aggregating differences based upon bounded measures such as mean proportions?

Background and Problem In the past, I have read or conducted meta-analyses that aggregate effects based upon mean proportions. For example, in a typical psychological experiment dealing with human ...
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### How can I compute a log odds ratio for a within-subject design that could be meta-analyzed with log odds ratios from between-subject designs?

Background and Problem I have a question concerning a meta-analysis combining effects from between- and within-subject designs using log-odds ratios (OR) as the metric of interest. I am familiar with ...
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### Why does the effect size for repeated measures ANOVA that do not assumed sphericity, is calculated using sum of squares of when sphericity is assumed?

The effect size index that I am referring to is omega squared. Omega squared is calculated using sum of squares values. When sphericity is violated in repeated measures ANOVA, you may used Greenhouse-...
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### Comparing effect of optimization on multiple runs with one variable

I have a problem with one variable (rounds) that affects the time it takes a program to solve it. For a given number of rounds I ...
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### Bayes factor for effect size

I need to construct Bayes Factor for testing: $$H_0: \quad 0 = \mu_t - \mu_c$$ $$H_1: \quad 0 \neq \mu_t - \mu_c$$ and my prior knowledge is modeled by distribution of effect size: \$ \delta = \...
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### estimating effect size with sMAPE in published results

I'm struggling to get the concept of effect size in the published forecasting literature. Most common metric that is used is the symmetric Mean Absolute Percentage Error (sMAPE). For instance see ...
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### Calculating effect sizes for meta-analysis. Which method to use?

I'm working on a meta-analysis, and I have a special problem regarding calculating effect size. Can anyone lend me some insight? I have a treatment and a control group, and for each group I have ...
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### Cohen's d for dependent sample t-test

Quick question: I've seen Cohen's d calculated two different ways for a dependent samples t-test (e.g., within-samples design testing the efficacy of a medication with pre/post timepoints). Using ...