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

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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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11 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
17 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
40 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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12 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
24 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
17 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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5 views

Estimate if effect sizes in a multi level model differ

I have the following model summary: ...
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13 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
55 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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8 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
23 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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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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30 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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2answers
73 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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10 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 ...
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1answer
19 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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23 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
28 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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13 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
49 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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24 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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17 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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37 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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50 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
54 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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31 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
115 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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19 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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1answer
48 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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3answers
61 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 ...
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47 views

Fixed effect not siginificant in multi-level model, what else to report besides significance?

I'm studying the effects of a teaching style intervention on student motivation. I use multi-level modeling since students are nested within teachers. The condition main effect is not significant (p = ...
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52 views

Interpreting intercept-only meta-analysis model when effect size is raw mean

Although I plan to use moderators to understand how the raw mean (and its sampling variance) is related to specific experimental conditions, I am curious: how would you interpret the intercept-only ...
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1answer
11 views

Standard effect size for assuming equal means

I do a community survey on a website once each year, I have data from the past two years and this year I'd like to remove questions which are getting similar answers each year. The survey questions ...
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41 views

Are you able to determine a effect size for GEE analysis using a multinomial, cumulative logit (SAS)

I am working on my discussion in my dissertation using a GEE model, multinomial, cumulative logit in SAS and I know I was not able to get a psuedo R but wondered if other ways to get an effect size. ...
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55 views

Is it possible to compute some measure of effect size from four means from a split-plot (both within- and between-subjects) 2x2 design?

For a meta-analysis, we are interested in the comparison of two groups. From the articles, we can extract four means: two baseline measures on one of our dependent variables, and two measures ...
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232 views

Consequences of exceeding sample size after determination of sample in power analysis

Challenge In our office, I have been involved in a discussion about sample size and its influence on effect size - can you help me out and explain further? Base When conducting a power analysis, ...
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121 views

chi-squared goodness-of-fit: effect size and power

How can effect size and power of the chi-square goodness-of-fit test be calculated such that: Effect size is linear and standardized (given effect size $E_{x^2}$, $0 \le E_{x^2} \le 1$) so that ...
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31 views

ARMAX / ARIMA models: Effect Size and R-squared

Is there an easy way in Stata to get the percentage of the variance explained by an ARMAX/ARIMA model (similarly to the adjusted R-squared in multiple linear regression)? Moreover, working with ...
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1answer
95 views

Dummy variables in multiple regression

Let's suppose I measure weights of eight male and eight female mice, from four litters, that were subjected to two different treatments: a and b Here are my data: ...
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80 views

Calculating the required sample size for a 2x2 repeated measures ANOVA?

I have conducted an experiment with two independent variables, each with two levels. I had one group of participants who were tested under four conditions. I have performed the ANOVA using SPSS, and ...
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46 views

Effect Size PDF (and Confidence Intervals)

I've already read this, which isn't very helpful. Consider Cohen's $d$ for two independent random samples $\{X_{1j}\}_{j=1}^{n_1=N}, \{X_{2j}\}_{j=1}^{n_2 = N}$, given by $$d = \dfrac{\bar{X}_1 - ...
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44 views

How to statistically compare two independent differences?

Three methods A, B and C are used to measure a continuous variable x for each subject in a study. There are two types of subjects in the study: type1 and type2. Difference between type xA1 - xA2 ...
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1answer
39 views

Best effect size statistic for ordered categories

I have ordered categories, and a prediction for the size of the categories. If the categories were unordered, I would use Cramer's V as a measure of the effect size. [Feel free to give an opinion on ...
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194 views

Effect size and bootstrapping in paired t-test

I have multiple paired $t$-tests, such as one giving results: $t_{14} = 2.7,\ p = .017$ Although people seem to do effect sizes in different ways in repeated samples, I have taken the mean ...
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Getting a very low Phi value for a 2x2 table with pretty large effect size?

The 2x2 contingency table looks like this Converted Didn’t convert Hi 220 1606 low 188 1881 The ratio of converters for Hi vs Low is 0.12 ...
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How to cluster/analyze effect sizes after meta-analysis? (meta-meta-analysis)

For a research project I compared persons with and without a specific disorder on basically every published outcome I could find. The idea was to get some sort of profile of this disorder (i.e. skills ...