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 effect sizes of two treatments from a large number of studies

I suppose this would be some kind of meta-analysis. I would like to compare the effect sizes of two treatments from a large number of published studies. I would like to show that the other treatment ...
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1answer
10 views

How do I calculate effect size for percentages of totals?

I apologize if this questions is poorly worded or has a very simple answer but I work in a field very different than statistics. I am looking at diction (word use) in books from two different artistic ...
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19 views

Where does this formula for calculating pooled standard deviation for calculating Cohen's d come from?

On this page, it is said that the pooled standard deviation for calculating Cohen's $d$ can be calculated as $\displaystyle SD_{pooled} = \sqrt{\frac{SD_{1}^{2}+SD_{2}^{2}}{2}}$. Where does this ...
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1answer
16 views

Significance of a cluster with respect to the whole dataset

I mainly am a machine learning guy and my knowledge of statistics is a bit limited. I have a (small) dataset of objects described by two categorical variables: $$ \begin{array}{|l|l|l|l|l|} \hline ...
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1answer
78 views

Computing Paired Samples (pre/post) Effect Size with Limited Information

I'm conducting a meta-analysis using the Hedge's g effect size statistic. Many of the studies are only reporting: pre-treatment mean score pre-treatment standard deviation post-treatment mean score ...
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35 views

Interpretation of effect sizes

I made a conclusion after a lot of research on the internet and i want to know if it is sound in any way. Because i think i might have been thinking on this way too long. Here's the deal: we did an ...
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1answer
36 views
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14 views

Calculating effect size for model with incidence rate ratios?

I've got IRR from a GEE negative binomial with log link. I have within subjects effects (pre to post) and between subjects (difference in change between groups), how do I calculate effect sizes?
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19 views

Relation between variance stabilizing transformations and effect sizes?

When researching effect size for proportions, in particular the paper Effect-Size Indices for Dichotomized Outcomes in Meta-Analysis, that at least two of the usual effect sizes are realy variance ...
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26 views

R: Effect size from simple slopes

I have calculated simple slopes for a multiple regression using simpleSlope from package pequod(). Is there a way to easily compute an effect size for a single simple slope analysis from the output? ...
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9 views

effect sizes and significance

I had to do a two-way anova with as dependent variable a pretest to determine any pre-existing differences in the groups. It yielded one significant effect in with a low effect size η2= 0.046 and two ...
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1answer
35 views

How to show the Contribution of Independent variables in terms of percentage in Multiple regression?

I would like to show the independent variables (IV) contribution in percentage. For example, Regression equation is ...
2
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1answer
64 views

Calculating effect size (lnR) variances for studies with different study designs for use in meta-analysis

My question concerns the calculation of effect size variance for studies that are going to be included in a meta-analysis. I want to calculate variance so that I can weight each study by the inverse ...
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45 views

How can i calculate an effect size (cohen's d) from a linear random effects model (beta)

I am trying to figure out how to calculate a Cohen's d statistic for a linear random effects model. I did not do the analysis myself, I have read it in a journal article so i'm left to figure it out ...
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40 views
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1answer
79 views

Why is the p-value for Cohen's $d$ not equal to the p-value of a t-test?

I am using the package compute.es in R to calculate effect size from a $t$-test. The $t$-test is marginally significant with $p=0.05657$. When I run ...
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27 views

Two-way MANOVA - Total Effect of Independent Variables on Response Variables Together

I have run a two-way MANOVA in SPSS. In the model, there are two fixed (independent) variables A and B, and two response (dependent) variables X and Y. I am trying to ascertain the total effect of A ...
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1answer
31 views

Computing the true effect size from F-values and sample sizes?

I'm trying to extract a bunch of effect sizes from a couple of different studies in for which the authors have performed ANOVAs on their data. More specifically, I'm interested in the main effects of ...
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71 views

Interpreting partial eta squared and reporting it apa style

How do you interpret and report partial eta-squared in a two-way anova? I have run a two-way anova to inspect whether gender and level of education interact to have an effect on positive affect. ...
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15 views

Difference between measured factor, manipulated factor, covariates.

I am trying to understand this paragraph, and it would be great to have some extra clarity on what is meant? I'm trying to assess whether i can use this formula for collecting data for a ...
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4answers
3k views

A psychology journal banned p-values and confidence intervals; is it indeed wise to stop using them?

On 25 February 2015, the journal Basic and Applied Social Psychology issued an editorial banning $p$-values and confidence intervals from all future papers. Specifically, they say (formatting and ...
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3answers
394 views

Are smaller p-values more convincing?

I've been reading up on $p$-values, type 1 error rates, significance levels, power calculations, effect sizes and the Fisher vs Neyman-Pearson debate. This has left me feeling a bit overwhelmed. I ...
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0answers
16 views

Calculation of effect size for a mediation analysis with a dichotomous DV

I am using Haye's PROCESS macro to calculate the indirect effect (mediation) using a continuous IV, continuous mediator and a dichotomous DV. Haye's macro does not calculate an effect size for ...
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26 views

Best effect size estimator in simple linear regression?

Using a metric developed by someone else, I have calculated vegetation condition scores from a set of measured variables (about 1000 sites). I am using simple linear regression to determine how ...
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15 views

Determining the effect size using GPower

I have three ponds and would like to know how many random samples of algae I need to collect within each pond measuring 7 response variables. I would like to see how each pond responds to the 7 ...
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3answers
154 views

Why do irrelevant regressors become statistically significant in large samples?

I am trying to better understand statistical significance, effect sizes and the like. I have a perception (perhaps its wrong) that even irrelevant regressors often become statistically significant in ...
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52 views

Which method should I use to combine the data of my studies?

I want to make a meta-analysis on household consumption expenditures elasticity data. In these studies that I've got; methods and regions and etc. varies according to studies. But at last, the results ...
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1answer
99 views

Effect sizes (eta-squared) with confidence intervals for linear models

STATA has recently implemented effect size calculations for regression models in their postestimation procedures measures of effect size in Stata 13. It takes a regression or ANOVA object as input, ...
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65 views

R code for standardized coefficents and model effect size using nlme

I have fit a longitudinal random effects model using nlme and I prefer nlme because I can get p-values. While working with a ...
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2answers
97 views

Statistical significance versus sample size [duplicate]

Statistical significance of a (variable in a) model grows with sample size. Citing Gilbert (1986): If one uses test statistics with constant size (i.e. a constant degree of confidence), almost any ...
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331 views

Effect size to Wilcoxon signed rank test?

Some authors (e.g. Pallant, 2007, p. 225; see image below) suggest to calculate the effect size for a Wilcoxon signed rank test by dividing the test statistic by the square root of the number of ...
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1answer
51 views

Can you add up effect sizes of two related variables (e.g. age + age$^2$) from a single regression model?

I am interested in the effect of age on outcome Y. I have two nested linear regression models to test linear and quadratic effects of age: Y= $\beta_0$ + $\beta_1$ some_covariate + $\beta_2$ Age + ...
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1answer
70 views

What measure of effect size in ANOVA has mode at zero under the null (unlike $\eta^2$ that does not)?

I encountered a weird effect when computing eta squared in ANOVA. Here is a short simulation to demonstrate it. I simulate $k$ groups with $n=10$ each, with all values drawn from standard normal ...
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1answer
50 views

Is there any possible method to calculate effect size in SPSS mixed model?

I run MIXED command for mixed model analysis of repeated measured data. However, there is no option or menu for estimate power(like partial eta in GLM) in mixed analysis. Is there any method to ...
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1answer
111 views

Multiple Regression - effect size

I want to calculate the effect size of a multiple regression. So far, I used Cohens $f^2$. Somehow, I wonder, if the effect size expressed by Cohens $f^2$ is an appropriate measurement. Let's assume ...
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139 views

How to test difference between standardized difference between means

On a data set I inherited, I calculated the standardized difference between the means of 2 groups, d, for each of 5 variables. All the data was collected from same set of about 175 people, with 35 in ...
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33 views

meta-analysis, effect sizes for standard deviations

Is there any possibility to calculate effect sizes for the differences of standard deviations of two groups? (Is there any possibility to calculate the difference in the standard deviation between two ...
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0answers
53 views

Can I calculate effect size using only % difference between means?

I need to calculate the effect size of a published experiment so that I can compare it to a replication attempt. However I have very limited information about the original experiment - only the mean ...
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61 views

When an effect size has to be considered sufficiently large?

I submitted a paper in which I analyzed the data by a mixed design ANOVA. I reported generalized eta squared as effect size. After significant interactions, I conducted planned comparisons. A reviewer ...
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31 views

Mixing ITT and TOT/LATE Effect Sizes in Meta-Analysis

I have a question concerning the coding of Effect Sizes for a large (educational) Meta Analysis with mostly latent outcome variables. Some studies provide "Intent to Treat" Data from which I ...
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1answer
63 views

Compare two distributions of large sizes and unequal variances where one distribution is heavily skewed

My data is from cells that are treated under two different conditions and then their response to the condition is measured by one output variable. The cell populations in the two conditions are quite ...
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22 views

Compute effect size based on simulation using different lists of different length

For my research purpose I wrote a small simulation to compute an empirial p-value based on an input gene list and a reference gene list. The idea is to check for each gene in the input gene list, the ...
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42 views

Definition of $\lambda^2$ effect size measure

In an article in the American Psychologist there is a series of bar graphs with a statistic next each bar. The statistic is described in the text and in the graph captions as being an effect-size ...
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1answer
942 views

Mann-Whitney U-test: confidence interval for effect size

According to Fritz, Morris, and Richler (2011; see below), $r$ can be calculated as an effect size for the Mann-Whitney U-test using the formula $$ r = \frac{z}{\sqrt N} $$ This is convenient to me, ...
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55 views

How do I convert Cramer's V to Cohen's d?

Say I have a chi-squared test that compares 3 different groups: $\chi^2_2 = 9.81$, $p=.012$, Cramer's $V=.33$ How would I go about converting this to a $d$-statistic? Is the proper approach in ...
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41 views

Can Hedges' d be used to compare unlike effects?

I've got a question related to the use of Hedges' d in a meta-analysis of insect fitness information. Here is a link (pdf) to the paper I'm working with. In the appendices, the fitness information ...
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32 views

Effect size for hypergeometric test

Given an urn with N genes, ugh - I mean with N balls, B of which are white, I can calculate the probability of randomly drawing b or more white balls in a sample of n using hypergeometric test. This ...
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1answer
20 views

problem: a sample size for the assumed effect in the 2 sample proportion test

I would like to calculate a sample size for the 2 sample proportion test when the significance level is assumed (0.05), power is assumed (0.90) and I'd like 2 sample proportion test to detect that ...
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32 views

Non-parametric effect size

Effect size, as estimated by Cohen's $\delta$, is: $d=\frac{\hat x_1 - \hat x_2}{\hat s_{pooled}}$ Since the numerator is an estimate of difference in location, and the denominator is an ...
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696 views

How to use delta method for standard errors of marginal effects?

I am interested in better understanding the delta method for approximating the standard errors of the average marginal effects of a regression model that includes an interaction term. I've looked at ...