# effect size

1. ### Sensitivity analysis said I wouldn't find an effect less than .8 but I did!

Hello! I ran a sensitivity analysis on G*power and it told me that for my independent samples t test (10 people per group, alpha = .05, power =.8) I wouldn't find an effect size smaller than d = 1.32. I then ran the t test and got a significant result with an d = 1.15 How is this possible?
2. ### How can I intepret the effect sizes of Cramer's V when DF is high (like > 20)?

Dear All, I am doing Pearson Chi Square analyses in SPSS. Besides looking at the Chi Square Sig. value I also want to look at Cramer's V to analyze the effect sizes. My dataset has 12 million observations na I found a value of 0.12 for the Cramer's V. Standards for interpreting Cramer’s seem to...
3. ### Sample size calculation for a one way anova (three conditions)??

Hi there, I am designing a study that compares three conditions (differences in glass shape) on one main DV (drinking rate) (as well as some secondary DVs). I want an adequate sample size to be powerful enough to test the primary hypothesis, that there will be a difference between the three...
4. ### Calculating and Reporting Effect Size for Fisher's Exact Test?

Hi everyone, I am writing a paper for publication. This is my first time doing a survey study, and also my first time working with categorical data (I, like many people unfortunately, have learned statistics bit by bit, as I have needed it in my research). The journal I am submitting to...
5. ### Post-Hoc Power Analysis (G*Power) for simple linear regression

Hey everyone! I conducted a simple linear regression with non-significant results. Now I would like to analyze the power of this calculation using G*Power. I chose the option "F-tests - Linear multiple regression, fixedmodel, R(2) deviation from zero and entered 1 as my numer of predictors...
6. ### Confidence interval for Cohen's H

hi everyone, I would like to create a Forest plot for a number of studies that looked at proportions. I calculated effect sizes using Cohen's H, but now I need to know the confidence intervals for those effect sizes. Does one of you know how to calculate those? Thanks in advance!
7. ### Effect Sizes

This may seem like a ridiculous question, but it's bugging me and no text book or paper I've read has answered it. I am looking into research on effect sizes and their use in research. I see a lot of mention of Cohen's D and F2 and the "small", "medium" and "large" effect sizes. Can someone...
8. ### Using Pre-Post data in a meta-analysis

Hello, I am trying to figure out the best way to calculate an effect size for a single-group design when I do not know the pair-wise correlation or standard deviation for the difference scores. I have received mixed messages as to whether or not I can use the formula for independent measures...
9. ### Repeated Measures Design & Effect Sizes, Normality

My question is about calculating effect sizes for a repeated measures design with a small sample size. I want to calculate Cohen's d.av (as recommended by Lakens, 2013 and others) instead of d.z (which you can compute using just your t-value and N), since the latter tends to overestimate your...
10. ### Relationship between effect size, sample size and p-value?

Is there a simple formula that links effect size, sample size and p-value? Specifically, how does the p-value depend on effect size and sample size? Are there any other critical factors involved in this relationship? I'm basically looking to understand how these factors are linked...

I'm a bit desperate for statistical help so trying out all avenues. Any guidance appreciated! I need to justify a sample size of 30 or 32 (15 or 16 per arm) for a placebo-controlled pilot clinical trial of a drug. This is all I can afford, but that is not a good enough justification for...
12. ### Using effect sizes to determine questionnaire sensitivity

Hi guys, I ran a therapeutic group with 6 people and got them to complete 5 questionnaires before the group and repeat them after the group. I'm now writing this up as a report and I know I can't carry out t-tests as the sample size is so small, but I have been advised to report effect sizes...
13. ### How to calculate sample size and effect size for comparing means from two groups

Hi all, hoping i can find some answers here for a bit of a problem i am having regarding a sample size calculation for a study I am soon to conduct. The population size is 64 and fixed. 32 control and 32 intervention. No drop outs will occur in this trial. There will be a pre (baseline) test...
14. ### Report effect size?

Hi, I am new to this forum and my knowledge about statistic is pretty basic. So beforehand I thank you for your help. In my research I used non parametric tests to compare two groups´ academic performance. It had a quasi-experimental design where the groups were not randomly selected but were...
15. ### What would you do if you had two very different Values of Cohen's D?

I conducted a factorial ANOVA.. and I found a significant interaction. I used two independent samples t-tests to conduct a further simple effects analysis one group always had higher accuracy than the other group regardless of the condition. However: condition 1 had an extremely...
16. ### Comparing the Power and Effect Size from Different Studies

Hi there Talk Stats Community, I am an undergraduate research assistant. Currently I am doing research on a project, and our results have indicated something that is quite different from previous findings. We have used a more specific and sensitive test to prove that a particular microbe...
17. ### Is there a difference between z-score and effect size?

I just started teaching statistics to myself (I never had it in school but will need it when I start University). I have problems with z-scores and effect size. I think that you use a z-score if you want to know how a score compares to the mean or standard derivation. And you use the effect...
18. ### Bigger sample size and less good results or smaller sample size but better results

I hope this is the right place to post this question. I'm doing my thesis based upon the data of my professors research study. I want to look into wether 2 different psychological treatment conditions affect social phobia compared to a control group, how they differ, and wether former...
19. ### power analysis- interpreting sample size given established literature

Hello and thank you for clicking, I am attempting to use relevant effects size from a published study to obtain a suggested sample size for my related study in G*power. However, 1) the previous study only compared 2 groups w/ t-test and I want to compare 5 with one way ANOVA and 2) the...
20. ### Power analysis (gpower) - interactions

I'd like to conduct a power analysis in gpower to determine the total N required in a study, with the following requirements: power desired: 0.80 alpha: .05 effect size: unsure what to use here (explained below) study design: 2x2 within subjects anova (4 conditions) where my main...