The effect-size tag has no wiki summary.
6
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0answers
625 views
Effect Size/Mean Squared Error from Linear Mixed-Model in R
I'm trying to report an effect size for a Linear Mixed-Model we've fitted in R. Right now I'm looking at reporting partial eta squared or eta squared. However, to do so I need to calculate the Sums of ...
3
votes
1answer
138 views
Am I using the wrong statistical test?
I am using $\chi^2$ to analyze a set of data gathered over 4 time periods. The two variables are independent--each 'event' is categorized as 'good' or 'bad'. We want to prove that the intervention ...
2
votes
1answer
107 views
Effect on a rate
I've got one independent variable and two dependent variables. As a concrete example, consider the independent variable to be browser (categorical, what Web browser a visitor to a Web site uses) and ...
2
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1answer
258 views
Is a biased or unbiased estimator used for pooled SD in calculating Cohen's d?
When calculating Cohen's $d$ for independent samples, you must use a pooled $SD$. However, I have seen both of these:
$$SD_{\text{pooled1}} = \sqrt{\frac{ (n_1 - 1)s_1^2 + (n_2 - 1)s_2^2}{n_1 + ...
5
votes
1answer
5k views
Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples)
I have a question for you all about calculating Cohen's d and pooled SDs.
1) one-sample / paired-sample vs. independent samples Cohen's d calculation
It seems that for calculation of Cohen's d (an ...
1
vote
1answer
200 views
Confidence Interval for $\eta^2$
Following my question here, I am also looking at the difference between males and females and I have conducted linear regression in a general linear model setup for this purpose.
My effect size for ...
6
votes
2answers
418 views
Whether to report confidence intervals of effect sizes such as $r$ and $\eta^2$?
I have calculated the bivariate linear correlation coefficient between $x$ and $y$ and it is $r= 0.45$; $p<001$.
I know $r$ is a measure of effect size.
Should I also be reporting the ...
1
vote
1answer
253 views
Effect size and signal detection
Are d prime (d') in signal detection theory and Cohen's d (mainly reported in the context of the general linear model) measures for the same thing (i.e., the difference of the means in SD-units), and ...
2
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0answers
181 views
Does pooled variance correct for/protect from unequal variance when calculating effect size?
This may be a lame question, but I got stuck and can't get my head around it. I am running a gene expression analysis, comparing ~10000 genes between two groups, n=6 samples per group. My pipeline ...
4
votes
1answer
3k views
What is the pooled standard deviation of paired samples?
I am trying to do a priori sample size calculation based on published results. However, I am unable to obtain a reasonable estimate of the published effect size (which is not reported) as I am unable ...
1
vote
0answers
91 views
How to compute effect size for different measures of association?
My colleagues and I are looking for guidance on how we might compute a common effect size (ES) from the following measures of association:
Pearson's r
Spearman's rho
Kappa
ICC / intraclass ...
1
vote
1answer
39 views
Can the influence of a different factor on a known effect be analyzed directly?
If I am trying to analyse wether a known effect is inhibited by another factor, is it a fallacy to analyse the influence of the factor on the effect size directly? I.e. can I just use a statistical ...
2
votes
1answer
426 views
Cohen's d for 2x2 interaction
I have a significant 2x2 interaction in a between-subjects design. I would normally report omega-squared as my effect-size measure, but I've been asked to provide Cohen's d instead? Can Cohen's d be ...
3
votes
0answers
164 views
How to assess whether two treatments are significantly different using Cohen's d (effect size)?
Cohen's d is a measure of effect size calculated as:
$d = (x_1-x_2) / \sigma_{\text{pooled}}$
where $x_1$ is the mean of one group, $x_2$ is the mean of a second group, and $\sigma_{\text{pooled}}$ ...
4
votes
3answers
552 views
Effect size and statistical significance
Using Cohen's d, I am getting small amd medium effect sizes for results that are statistically non-significant (p>.05). Does this make sense?
5
votes
0answers
313 views
Is the Binomial Effect Size Display (BESD) usually an unsound, misleading technique?
It's hard for me to accept that Donald Rubin would ever come up with a true lemon of a technique. Yet that's my perception of the BESD [1, 2], 3]3. He and Robert Rosenthal (1982*) claimed that there ...
1
vote
2answers
577 views
$\eta^2$ and paired t-tests
When doing a paired t-test, is it appropriate to use the paired t value to calculate $\eta^2$?
I ask because it is not appropriate to calculate Cohen's d based on the paired t value.
Thanks.
1
vote
1answer
210 views
Interpreting effect size
One of the most widely used interpretation of effect size is Cohen's $d$, as follows:
$<.10$: trivial
$[.10,.30]$: small to medium
$[.30,.50]$: medium to large
$>.50$: large to very large
...
2
votes
1answer
523 views
Effect size for Fisher's exact test?
Does anyone know a way to calculate the effect size of a Fisher's exact test? Does that even make sense?
Thanks
1
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0answers
702 views
How to calculate Cohen's d effect size intervals for a within-subject design?
I have looked at different web tools for calculating confidence intervals for effect size like Cohen's d for within-subject design. My experience from this survey tells me that there are different ...
2
votes
2answers
307 views
Quantifying effect of a categorical variable in time series analysis
I have a dependent variable ($y$ axis in the pictured graph) trending over time ($x$ axis). I also have a categorical variable, which was constant until one point in time, then changed to another ...
1
vote
2answers
174 views
Reporting $R^2$
Following my question here, when is it appropriate (or inappropriate) to report r squared for a bivariate linear correlation.
As explained in the earlier question, r = 0.74 which results in r squared ...
2
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1answer
227 views
Effect size interpretation
If r between X and Y is 0.74, then r-squared is 55%.
According to many 'rules of thumb' and others, the effect size (in this case r) is considered 'moderate' or 'medium'.
As such, only 55% of the ...
4
votes
0answers
462 views
Effect size measure for doubly-repeated measures design?
Update:
I haven't gotten any answers, so I am simplifying my question. Say I measure test scores of $100$ people in one of two conditions. Each test has $10$ items. On each item, each person can ...
3
votes
1answer
379 views
How to calculate sample size per condition if given overall df? and How to calculate Cohen's D given mean, t, standard error, and df?
I'd like to calculate effect sizes using data from a published study. The aggregate sample size is provided but not the sample size for each of the three experimental conditions.
Is there a way ...
3
votes
1answer
916 views
How to calculate 95% confidence intervals for partial eta squared and eta squared?
Following on from this question on reporting eta squared, I would like to report 95% CIs for my effect size point estimates (partial eta and eta squared values).
What statistics do I need to know ...
3
votes
1answer
245 views
Using ANCOVA with data matched on propensity scores
I've read papers comparing them, but never seen a study that used them
together. Is this done? Why or why not? Suppose you use
ANCOVA to analyze a reduced sample of matched pairs generated using
...
-1
votes
3answers
224 views
Magnitude of a relationship
If I run Pearson correlation between Variable A (buyer/nonbuyer of ice-cream) and Variable B (buyer/nonbuyer of yoghurt) and have:
Ho as "There is no relationship between...."
Ha as "There is a ...
4
votes
1answer
772 views
Effect size calculations in mixed ANOVA design for power analysis
I need to calculate effect size for a mixed ANOVA design. I need it because I'm using GPower3 to calculate a rough sample size for a full study. I have pilot data. Based on this page:
...
3
votes
1answer
537 views
Some doubts about using GLMM
I'm analyzing the results of a hormone manipulation experiment. I measured a number of variables at three times in three groups. The groups are different sizes and not all individuals were measured ...
2
votes
1answer
325 views
Effect size for rectangular frequency table
I have run several Chi-square tests and want a measure of effect size. I have some 1x2 tables, 1x4 tables, 4x9, and 3x4 tables of frequency data.
What measure of effect size can I use on these ...
3
votes
1answer
1k views
Recommended effect size measure for repeated measures t-tests and repeated measures contrasts on experimental data
Context
This came up recently in a consulting context. A researcher was performing repeated measures t-tests based on experimental data.
Some of the analyses involved comparing one condition with ...
5
votes
1answer
502 views
Effect size of Cochran's Q
I have performed a Cochran's Q test for a within-subjects experimental design with 3 conditions and 36 participants with a dichotomous dependent variable.
I found a (just) statistically significant ...
5
votes
1answer
910 views
How do I calculate the effect size for the Kolmogorov-Smirnov Z statistic?
is there a way of calculating an effect size for the Kolmogorov-Smirnov Z statistic (in SPSS or by hand)? Or should I stick to the Mann-Whitney test, even though my group sizes are less than n=25?
7
votes
3answers
1k views
Effect size for interaction effect in pre-post treatment-control design
If you choose to analyse a pre-post treatment-control design with a continuous dependent variable using a mixed ANOVA, there are various ways of quantifying the effect of being in the treatment group.
...
9
votes
3answers
459 views
What does it mean for a study to be over-powered?
What does it mean for a study to be over-powered?
My impression is that it means that your sample sizes are so large that you have the power to detect minuscule effect sizes. These effect sizes are ...
2
votes
1answer
336 views
Alternative Egger's test, without using standard error
A simplified regression equation $ES=\frac{a+b}{n_1+n_2}$ has been suggested as an alternative to Egger's regression equation $\frac{ES}{SE}=\frac{a+b}{SE}$, where ES=Effect Size, $n_1$=sample size of ...
10
votes
1answer
611 views
Do likelihood ratios and Bayesian model comparison provide superior & sufficient alternatives to null-hypothesis testing?
In response to a growing body of statisticians and researchers that criticize the utility of null-hypothesis testing (NHT) for science as a cumulative endeavour, the American Psychological Association ...
3
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2answers
1k views
Evaluating effect sizes of interactions in multiple regression
I have been running 3-level multilevel models with HLM, and my main interest is in some cross-level interaction effects that I am finding. My concern is that the effect sizes of these interactions ...
3
votes
2answers
2k views
Effect size of Spearman's rank test
I know that $r$ is itself a measure of the effect size, but I would like to know if using Spearman's rank test I can argue that the relation between X and Y is significant with $r = 0.33$ and that the ...
6
votes
3answers
5k views
Linear regression effect sizes when using transformed variables
When performing linear regression, it is often useful to do a transformation such as log-transformation for the dependent variable to achieve better normal distribution conformation. Often it is also ...
4
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2answers
3k views
How does one calculate Cohen's d and confidence intervals after logit in Stata?
How does one calculate Cohen's d and confidence intervals after logit in Stata?
3
votes
2answers
1k views
How to use STATA to pool Cohen's d?
I am attempting to calculate Cohen's d and then pool those estimates into a summary effect size. Can anyone help? (STATA or SPSS software owned).
7
votes
2answers
816 views
Intraclass correlation and aggregation
Imagine that:
You have a sample of 1000 teams each with 10 members.
You measured team functioning by asking each team member how well they think their team is functioning using a reliable multi-item ...
