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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28 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
101 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 = z/√(N) This is convenient to me, as I report r also ...
3
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0answers
23 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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0answers
21 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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0answers
14 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
15 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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0answers
20 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 ...
6
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1answer
201 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 ...
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0answers
8 views

Statistical comparison of 2 dependent cohen's ds

How would I statistically test the significane of the difference between two Cohen's d derived from different tests within the same sample? Specifically, in my neuroimaging data metabolism in brain ...
1
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1answer
46 views

Effectsize difference between Mann-Whitney U and t-Test

I have data that is officially not normally distributed (Kolmogorov-Smirnov test < .000 BUT N=around 1200 so K-S not really reliable). In plot I can see that form looks good but negatively skewed. ...
4
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2answers
78 views

Effect size for a one-sample t-test

Imagine I work in a screw factory (which is not true). We have been producing a series of 5cm-long (on average) screws for years. I want to modify the production parameters in order to save some money ...
0
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1answer
25 views

Effect sizes for post-hoc paired comparisons in one-way ANOVA

Is there any alternative (like Cohen's d in t-test) to report about effect sizes for post-hoc paired comparisons in a one-way ANOVA (3 factor levels, correlated samples)?. Many thanks!!
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1answer
67 views

Interaction terms and effect sizes in multiple regression

I know there are similar questions on here, but I can't quite find an answer that covers all of what I need. I am running multiple regression in r with two predictor variables and sometimes an ...
7
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1answer
308 views

Why is usually the acceptable probability of type 1 and type 2 errors different?

This question is raised by my supervisor and I don't know how to explain. Usually the accepted confident level is 0.95 which means that the probability of type 1 error is 5%. But the usually ...
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0answers
55 views

Effect sizes in within-subject design on R

I'm doing a meta-analysis but I need your precious help on couple things : 1) First, on R, in the compute.es package, I found only effect sizes computation formula ...
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1answer
41 views

When testing for a difference between effect sizes, is test power affected by their respective magnitude?

When comparing two effect sizes with a statistical test, does it matter for the test's power whether these effect sizes themselves are large or small? Imagine you are planning an experiment in which ...
3
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1answer
97 views

How to get proper effect size from LMM?

I now have a problem with effect size of LMM. Someone insisted that I should have effect sizes after p values. I then thought that I can use 'estimate' in the output of pairwise comparison using ...
0
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1answer
19 views

How are these negative values understood?

I can't find literature to understand this table. What I know doing my research is that an effect size should be between 0 and 1. when 0.2 is slow, 0,5 medium and 0.8 and higher , high. But In an ...
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0answers
25 views

Mann-Whitney U test [closed]

I am comparing 2 separate datasets with the Mann-Whitney U test. I am analyzing three separate parameters present in both datasets and want to know which parameter gives greatest separation between ...
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0answers
70 views

3 way mixed ANOVA & pairwise comparisons effect size

im in desperate need of some help for my data analysis assignment! I have a 3 way mixed anova- where I have 2 sig main effects, one significant two way interaction and the sig three way ...
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1answer
74 views

Calculating effect size (partial eta squared) for a planned comparison effect

I have a between-subjects ANCOVA (factors A and B, and covariate C), for which A*B is significant. I decomposed the interaction with a planned comparison described by the contrast A=(-1,1), B=(0,1), ...
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1answer
87 views

How to perform a meta-analysis of studies without a control group?

I want to meta-analyse some studies which I've already collected and review. However, the studies did not used control groups, due to the types of questions used. How can I do the meta-analysis or ...
2
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0answers
59 views

Is there an effect size for Kappa's?

I am staring a project on comparing standard ways of creating a classifier with some heuristic methods. The heuristic methods should result in a faster training for the classifier but should result in ...
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0answers
19 views

What is a “concordance score” for regression coefficients?

I came across this "concordance score" in a set of slides called Penalized regression methods for ranking variables by effect size, with applications to genetic mapping studies, by Ji Zhu: $$ ...
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3answers
55 views

Does the order of magnitude of sample values influence p-values and effect size?

When using an independent-samples t-test to compare two variables, do the absolute values of the samples affect the test statistic and the effect size? In other words, is it easier to obtain ...
2
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0answers
45 views

Statistically correct to compare two Spearman's $\rho$-Vaules?

I have different variables (A, B, C, D) which are all ordinal scaled. I have another variable (Z) which is ordinal scaled, too. My sample size is approx. 1.500. Is it in the statistical sense ...
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2answers
203 views

Calculating effect sizes and standard errors for the difference between two standardized mean differences

I have two related questions, both of which are related to a meta-analysis I am performing where where the primary outcomes are expressed in terms of the standardized mean difference. My studies have ...
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0answers
61 views

Calculating Hedge's g and its variance from t-statistic

I believe there is a way to calculate Hedge's g and its variance from a t-statistic. I have found the formulas to calculate Hedge's g from one-sample t, and from independent groups t. one sample: ...
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0answers
32 views

Obtaining Cohen's d from z-test statistic

After an ANOVA, I run post-hoc tests with the glht function in the multcomp package. glht ...
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3answers
98 views

Understanding $\chi^{2}$ and Cramér's $V$ results

I have two groups of buyers, A and B, and I want to test whether the difference between the percentage of them who would buy a ...
0
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0answers
43 views

Effect sizes from regression analysis and factor loadings

To do a meta analysis, I try to calculate effect sizes. In an article by Shah and Ward, the authors do a regression analysis after combining various factors by a CPA to four factors. The factor ...
0
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0answers
33 views

power analysis when mean and standard deviation are given

I have been asked to perform a sample adequacy test (i.e., I suppose, to verify what is the minimum difference that can be quantified between two grous) where a new sample (of which mu, sigma and ...
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0answers
23 views

simulate ANOVA data to follow a specific eta-squared

I am simulating RM-ANOVA data with three treatment conditions (one-way within subjects designs). I would like to be able to add an effect to the data so that eta-squared has a specific value. ...
0
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1answer
72 views

Question about EFFECT SIZE

I have a question. If I found the effects of a variable is insignificant (p>.05), but the effect size d is 0.2 (small effect). So I used GPower to calculate the power and I found it is 0.14, which ...
3
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2answers
50 views

What are real strengths of association when using Pearson correlation?

I have located a table that breaks downs Pearson's correlation values into 3 categories. See below: My question is this. One could have a large positive correlation of 1 as well as a perfect ...
0
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0answers
76 views

eta squared and partial eta squared: do they have the same effect size categorization (by cohen)?

I was computing partial eta squared for an ANOVA. I can only find a categorization for eta squared which are either 0.02 (small), 0.13 (medium), 0.26 (large) or .001 (small), .06 (medium) or .12 ...
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0answers
41 views

after using AIC, how to determine the contribution or effect size of a individual covariate?

I am confused and looking for advise. I have found myself in this same situation repeatedly in the last few months. I want to know if covariate X is influential or important. However, I also ...
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0answers
19 views

MLR equivalent for repeated measures, multiple correlated responses

I'd like to determine the best approach to determining effect sizes for a set of experimental data with multiple correlated responses. Due to repeated measurements and high correlation between ...
1
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1answer
33 views

Using two one variable linear regressions on a single response variable to compare explanatory variables

I ran two single variable linear regressions $A$ and $B$. $A$ had a relatively large effect size $R^2$ = $.68$ while $B$ had $R^2$ = $.10$. Regressing the explanatory variable from $A$ (= $a$) on ...
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1answer
47 views

Designing Frequentist A/B Experiments

What parameters should one pre-specify before designing/running an experiment? (e.g. a two-sample, one-side, t-test) My understanding is that on establishes: Null hypothesis Maximum Significance ...
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0answers
40 views

Estimating Sample sizes for Null Hypothesis Testing

Wikipedia has the following table for computing sample sizes:                                       ...
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0answers
27 views

Moderator Sample Size Discrepancy in Meta Analysis

I'm coding a meta analysis and have come across a paper that seems to have significant variation in the number of participants who answered specific demographic questions. The total sample size is $N ...
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1answer
45 views

Pre-post treatment design: accounting for reduced effect of treatment in baseline high scorers

I'm planning a study in which I want to test the effect of a treatment on a dependent psychometric variable. I expect subjects who score lower at baseline to benefit more from the treatment (larger ...
8
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1answer
139 views

When/why does the central tendency of a resampling simulation markedly differ from the observed value?

Should one always expect the central tendency (i.e., mean and/or median) of a bootstrapped sample to be similar to the observed value? In this particular case I have responses that are distributed ...
2
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1answer
41 views

Proportionality of significance and effect size

Is it true that, given a fixed sample size N, it can be said that some measure of effect size and the measure of statitical significance (e.g., 1-p) are proportional? In other words, that, when ...
4
votes
1answer
72 views

Calculating CIs for $\eta^2$ via Z scores - sample size?

In the thread Confidence Interval for $\eta^2$ it was proposed that if only limited statistics are available (in my case, F, df1, df2, means), one could calculate the 95% CI for $\eta^2$ by: ...
0
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1answer
32 views

Good Literature on effect sizes

reporting effect sizes is pretty common nowadays, but I couldn't yet find any good book that compares different effect sizes values (d, g, r, etc.). I know the article by Rosnow and Rosenthal (2009), ...
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0answers
49 views

Effect size for indirect effect with a binary outcome

Is it possible to obtain the effect size of a mediation with a binary outcome? I am looking to report an effect size specifically for the indirect effect. I have already reported the effect sizes of ...
3
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1answer
712 views

How to convert from Mann-Whitney U to Z (or other effect size)?

I'm looking at multiple studies. I do not have the original data. One study I'm looking at provides means, standard deviations, and Mann-Whitney $U$ values (with $p$). (How) can I convert from ...
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2answers
60 views

When are odds ratios worse/better than risk ratios as measures of the effect size of associations between categorical variables?

Wikipedia gives some information on this. However, I seek more detailed information on when odds ratios/risk ratios are better, and why one is better than the other in certain circumstances.