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

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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
60 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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12 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
23 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
40 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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38 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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1answer
31 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
9 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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12 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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1answer
48 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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1answer
218 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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80 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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24 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
84 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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35 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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34 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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43 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
36 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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1answer
150 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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6 views

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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39 views

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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15 views

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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5answers
1k views

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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17 views

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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29 views

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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17 views

Influence of dimensions on volume

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}, ...
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1answer
66 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 ...
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1answer
39 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 ...
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22 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 ...
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1answer
83 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 ...
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1answer
56 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 ...
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37 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 ...
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41 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)} ...
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53 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 ...
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255 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 ...
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12 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 ...
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29 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 ...
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1answer
35 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 ...
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1answer
45 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: ...
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24 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 ...
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3answers
1k 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 ...
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133 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}, ...
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119 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 ...
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58 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 ...
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45 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 ...
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74 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 ...
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58 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 ...
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29 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: ...
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189 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 ...
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1answer
134 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 ...