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

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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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298 views

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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50 views

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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29 views

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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10 views

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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9 views

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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1answer
86 views

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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1answer
16 views

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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1answer
21 views

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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10 views

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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1answer
24 views

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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35 views

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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15 views

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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21 views

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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1answer
53 views

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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2answers
38 views

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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6 views

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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21 views

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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14 views

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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1answer
42 views

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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1answer
49 views

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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28 views

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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1answer
49 views

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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1answer
22 views

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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6 views

Estimate if effect sizes in a multi level model differ

I have the following model summary: ...
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23 views

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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1answer
79 views

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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12 views

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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1answer
27 views

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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94 views

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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31 views

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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93 views

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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14 views

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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20 views

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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30 views

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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20 views

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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1answer
31 views

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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20 views

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 ...
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1answer
59 views

How do I calculate the Credible interval of the effect size? (Bayesian framework)

I use R. I have a linear mixed model and I use its output to estimate my posterior distribution (with uninformative priors) using the function sim. I calculate the ...
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35 views

Cohen's d for interaction term in multiple regression

I'm conducting meta-analysis with Cohen's d as the primary effect size. One study predicts and finds an interaction of a continuous moderator variable and a dichotomous grouping variable (treatment ...
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19 views

Using effect size to calculate minimal detectable difference

I am trying to estimate minimal detectable difference in a proposed study. My question is, can this be done using the estimate for effect size? And if yes, how should it be done. Please tell me if ...
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58 views

Cohen's d for unequal variance

I know my two samples have unequal variance. Should I consider this in my calculation of the effect size? I'm using Cohen's d, which Wikipedia defines as $d = \frac{\bar{x}_1 - \bar{x}_2}{s}$ with ...
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56 views

What are Cohen's rules of thumb for interpreting $η^2$?

I'm aware of the limitations of these simple rules of thumb, but in the research context in which I'm currently working, I can't avoid them. This Cambridge University website cites the rules of thumb ...
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3answers
58 views

Does the logic of “family-wise error” apply to effect size estimation?

Background: As I understand, family-wise error refers to the inflation of Type I error when performing multiple hypothesis tests. For example, if I were to perform multiple post-hoc comparisons ...
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54 views

Effect size simple slope analysis

I want to calculate the effect size of a simple slope regression. The Dependent variable is a Questionaire score. The Independent variable is Hormone A The Moderator variable is Hormone B. Now I ...
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23 views

Meta-analysis on positively transformed effect sizes

I want to assess whether or not a wide range of animal behaviours in experimental studies change from control responses. As such, I want to compare absolute changes, rather than increases (+) or ...
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1answer
136 views

Effects size calculation for fixed factors in GLMER

I'm running a GLMER with two categorical fixed effects, their interaction term, and one categorical random effect. Can you suggest/explain a technique for calculating the effect size of the fixed ...
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23 views

interpreting the “effect size” of standardized regression coefficient

Is there a reference I could use to say how large the standardized regression coefficient is? For example, a 0.25 SD change would be "small" effects? Thanks!
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62 views

Effect size (cohen's d) when mean and SD are zero

I am calculating effect sizes (Cohen's d) for a meta-analysis to examine pre-test to post-test differences after receiving a word-learning treatment. I am using pre-test and post-test means and SDs in ...
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84 views

Is there an effect size for a single proportion?

I want to conduct a meta analysis of the incidence rate of the complications of a specific disease. Studies report these complications as 4 patients died or 2% died. And there are no comparable group....