# 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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### 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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### 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 difference ...
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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 ...
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### 2 sample t-test - Calculating sample size

Suppose I have two samples that are the same size and are made of the same constituents such that element ai in sample A corresponds to sample bi in sample B. The sample A represents the group before ...
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### What is effect size… and why is it even useful?

I have an introductory-graduate-level statistics background (assume I know mathematical statistics and probability at an undergraduate level (e.g., Wackerly et al., Ross' Probability), and have some ...
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### Effect size in two way ANOVA

I'm writing my discussion section for my report and I have got the effect size but I just don't know how to discuss them in my discussion. My main effect for factor 1 is sig which is the effect of ...
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### Comparing effect sizes across different data sets with non-normal data

I want to conduct a comparative analysis across a large amount of studies by looking at the effect sizes of their results with another variable. I am not too familiar with effect sizes so I'd ...
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Question: We have $n$ dimensional box with length of dimensions equal to $(x_{1,1}, x_{1, 2}, ..., x_{1, n})$ and we squezee/strech it to obtain another n dimensional box with dimensions $(x_{2,1}, ... 0answers 25 views ### Cliff's Delta or Vargha-Delaney A? We have two sets of non-paired numbers, and we wanted to know if they were different, and if so, how different they were. To that, we used Wilcoxon, which told us they were different (we got a ... 1answer 30 views ### Transforming Cohen's d effect sizes into unit changes I want to calculate unit changes (or percentile changes) from an intervention for a continuous outcome variable where I have the pre and post test means and standard deviations. From that I can ... 0answers 14 views ### How does power change with small changes in mean (and effect size)? So for the following groups, Group A has the (n=50, mean=50, sd=10) Group C has the (n=50, mean=53, sd=10) Group D has the (n=50, mean=54, sd=10) Group E has the (n=50, mean=55, sd=10) I have ... 1answer 42 views ### Combining multiple outcomes in studies (no meta-analysis) I'm looking for a way to combine effect sizes (mean difference) and variances for several single studies but I don't want to conduct an overall meta-analysis. That means I'm only looking for an ... 1answer 40 views ### Effect size of a binomial test and its relation to other measures of effect size I would like to find the effect size of a binomial test and relate it to other measures of effect size such as Cohen’s d or Pearson’s r. Say I have 13 successes for 18 trials, where the probability ... 0answers 36 views ### All effects are 20%. Does this fallacy have a name? My old biophysicist friend told me that they used to joke that all effects are always 20%. For instance, they'd test a diet, and find that eating less salt increases life span by 20%. If they test ... 0answers 28 views ### Confidence of Effect Size Differences Hedges and Olkin (1985) suggest the following procedure for computing confidence intervals for Hedges' g resp. d $$\text{CI} = g \pm 1.96 \sqrt{(n_2+n_1)\big/(n_2n_1) + g^2 \times .5\big/(n_1+n_2)} ... 0answers 42 views ### Can I calculate effect size using F, p and N (sample size)? I need to calculate the likely/possible effect size of my study for a research proposal, based on the effect sizes of previous studies. The end goal is to determine the sample size needed for ... 0answers 96 views ### How to calculate effect size Kappa Squared for multiple parallel mediators? I was using the function mediation() from the package MBESS to calculate κ2 (kappa squared) as the effect size for a single mediator model. How can I calculate κ2 ... 0answers 8 views ### Pre and multiple post (after, 6m 12m) on secondary outcomes. How to get effect sizes and CI? Writing a paper on pain improvement as the primary outcome. Comparing 3 treatments with a control group that has no post data. Interested in physiological variables as secondary outcomes such as ... 0answers 14 views ### Effect size for difference between variances / Levene's test I have tested a hypothesis of equal variances (using Levene's test), and would like to report an effect size alongside the significance test. Unfortunately, I cannot seem to find any references to a ... 1answer 30 views ### Report effect size after regression of z-scores? I was wondering what (if any) the benefit is of reporting effect sizes (e.g., eta-squared) after running a regression model in which the dependent variable is z-transformed. In such a model, the ... 1answer 26 views ### How to compare the effect size of two significantly different mixed liner models computed by lmer? I have two "unrelated" data frames (df1, and df2). The type and number of columns and rows is identical, just the actual data differs. I am fitting the same base and full models over both: ... 0answers 23 views ### What size standard deviation is considered uncommonly large or small? [duplicate] What does the size of the standard deviation mean? For example, if I want to study human body size and I find that adult human body size has a standard deviation of 2 cm, I would probably infer that ... 3answers 673 views ### What does the size of the standard deviation mean? [duplicate] According to Wikipedia (my emphasis), In statistics, the standard deviation ... is a measure that is used to quantify the amount of variation or dispersion of a set of data values. A standard ... 0answers 110 views ### Effect-size of treatment on a categorical variable? I'm performing an A/B test where the variable of interest, X has N > 2 levels, (i.e., X \in \{1, 2, \ldots, N\}), and the data I'm collecting should be pretty standard:$$\{x^c = (x_{1}^{c}, ... 0answers 75 views ### R packages to calculate Effect Size There are several R packages with functionality to calculate effect size. Recently I start to use the package pwr. Taking ... 0answers 42 views ### How to get an effect size in nlme? I have recently been asked to provide an effect size for a mixed-effects linear model which I had fit using nlme. After doing a lot of hunting, it's become clear that effect size with mixed models is ... 0answers 35 views ### Testing if two variables have significantly different effects on the data I'm looking for a way to test if two variables have significantly different effects on my data. I'm also interested in a way to test if they have the same effect. Currently, I'm jointly calculating ... 0answers 40 views ### How to calculate the effect size after Welch ANOVA? I used oneway.test() because Levene's test indicated heterogenity of variance. Unfortunately, I don't know how to calculate the effect size now. Does anybody have ... 0answers 39 views ### Bootstrapping effect size measures in a repeated measures design A journal that people in my lab are submitting to asks for confidence intervals for effect size measures. We have a$(3) \times (3)$design where each subject completes 3 blocks of trials, containing ... 0answers 19 views ### Determining partial eta squared from an anova table without SS error I was given the following information and asked to calculate partial eta squared: ... 0answers 122 views ### How to calculate the sample size for proportions using Effect Size? I need to determine the sample size for my experiment. In my experiment I will select a set of x projects, from a population of N project. For the sample x projects will apply a treatment to know the ... 1answer 83 views ### How do I convert$\eta^2\$ to Pearson's r?

I am doing a meta-analysis of associations between sets of variables that are essentially all continuous. However, many studies operationalised them at 'lower' levels, and I have (converted to) most ...
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### Is covariance a measure of effect size?

Is covariance a measure of effect size? Since correlation is such a measure, and correlation is normalized covariance, I would think so, but I'd like to know for sure.
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### Perfect separation of two groups but rs is not 1

I have a dichotomous variable (group 1 and 2) and an ordinal scaled variable. The values of the ordinal scaled variable for group 1 are always lower than those for group 2: As I understand it, this ...
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### Calculating effect sizes for mixed effect logistic regression to determine subsequent sample size

We conducted a previous preliminary study using 40 participants. We analyzed the data using the lme4 package in R to conduct a mixed effect logistic regression. We ...
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### Cohens d effect sizes

I'm using Cohens d effect sizes as a means of providing a magnitude based inference in a study I'm conducting. I just wanted to clarify if I'm correct here: Anything between .0 and .2 is small. ...
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### Q-Test of Heterogeneity for only two effect sizes?

I am using the Q-Test of Heterogeneity to investigate if several effect sizes derived from two different studies are significantly different from each other. More precisely, I have, for every effect ...
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### Effect size for contrasts in hierarchical Bayesian “ANOVA”

Kruschke (2014) shows in his book how to compute posterior distributions of effect sizes (standardized mean difference) for the Bayesian analogues of frequentist independent-samples t-tests, and ...
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### Combining effect sizes in binary data

I'm working on combining effect sizes for a meta-analysis when one study reports multiple effects for the same construct. To accomplish this, I'm using the equation provided in the Borenstein ...
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### For Mann-Whitney, should I report effect size or Hodges-Lehmann pseudomedian?

When reporting a Mann-Whitney-U test result, is it better to report it's effect size or the Hodges-Lehmann pseudomedian (as R give us as "difference in location") ?
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### Two years of data with pre/post, need to figure out size of impact

I have 2 data sets: 2013-14 and 2014-15. Each year has pre and post data, measuring literacy. Sample size is 101 in one year and 93 in the other. I would like to determine if 2014-15 results were ...
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### How to compare explained variances of nested multivariate multiple regression models?

I have two groups of continuous* variables - let's call them MF (5 variables) and OR (2 variables), plus some demographics. It has been previously found that the MF are associated with one of the OR ...
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### Why do I get completely different Effect Sizes using same data but different methods?

When I calculate Effect Sizes (Cohen's d) on the same study using different methods I get completely different effect sizes. For example: (t=4.81, P<0.001, d=0.41) I also calculated d=0.41 using ...
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### Okay to use oneway ANOVA to compare these 3 group proportions from aggregated dataset?

My situation: I am assessing outcomes of a university course redesign. One of the goals of the redesign project was to increase successful course completion, as measured by a decrease in the course ...
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### How to calculate effect size confidence interval with multiple replications at multiple sites?

Let’s say we have an experiment at one location evaluating the effect of some sort of treatment on a control condition (n=4). We calculate the effect size as (Treated – Control)/Control*100. So for ...
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### How to calculate the effect size of differences in groups using dummies in multiple regression?

I am running a multiple regression analyses on a sample of 1800 respondents. The dependent variable is the mean of a 5-point likert scale and I have 6 predictors (antecedents) also using mean of ...
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### Effect size for goodness of fit chi-square

I would like to assess the effect size of a goodness of fit chi-square test. I have a variable that can have 3 states and test against a custom expected value. I used a variation Cramér's V for a ...
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### Categorical Predictors and categorical responses

I have a dataset consisting of 5 categorical predictors and a categorical response (class). I want to find out which predictor has an effect on the response. Additionally, I can't guarantee whether ...
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### How do I calculate the effect size for a Spearman's correlation? Is it the same as for Pearson's correlation?

I'm having trouble understanding how can I calculate the effect size for a Spearman's correlation. I have the following results: rho= .352, df= 83, p<.01. Thanks!