effect size

  1. K

    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...
  2. T

    please help me justify sample size for a pilot clinical trial

    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...
  3. B

    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...
  4. D

    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...
  5. V

    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...
  6. M

    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...
  7. M

    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...
  8. M

    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...
  9. S

    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...
  10. A

    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...
  11. N

    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...
  12. B

    Calculating effect size with interaction term

    If I am running multiple regression in r, what is the next step in order to get the effect size for all variables when there's also an interaction term in the equation. For example: model=lm(DV ~ Var1 + Var2 + Var2:Var3) Also, what's the best way to determine whether or not to do an...
  13. A

    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 responses, I know that a simple multiple linear regression model obviously isn't the answer. The...
  14. R

    Semipartial correlations for simple slopes

    Hello! I'm in need of some help for calculating sr2 for simple slopes. Here is my situation: I'm using SPSS. I have three IVs: x1: dichotomous and coded -1,1 x2: dichotomous and coded -1,1 x3: continuous centered variable I have a 3 way interaction that I've calculated the simple...
  15. S

    Meta-analysis: How should one handle non-significant studies containing no raw data?

    Let's say that I'm conducting a meta-analysis, looking at the performance of group A and group B with respect to a certain construct. Now, some of the studies that I'll come across will report that no statistical differences could be found between the two groups but no exact test statistics...
  16. M

    Paired T-test effect size

    Can someone please direct me to a calculation for an effect size for a paired samples t-test along with a reference? Thanks in advance.
  17. K

    Effect sizes and repeated measures

    Hi there, I am doing a bit of research looking at the effects of repeat test taking. Students are allowed to take a test multiple times. I have a dataset including student scores on each iteration of the test. I have done a repeated measures ANOVA to try to determine whether scores...
  18. A

    Post-hoc Power, effect size for Chi-square

    I need help with my post-hoc power analysis, specifically the effect size: I measure children's successrate under four conditions. My dependent variable is nominal (specifically binary, with the values 0 (failed) and 1(succeeded)) My independent variable is nominal with four categories. My...
  19. A

    Graphing Effect Size Comparions

    Hi! I would like to take a single school's achievement data (as an effect size) and plot that on a scatterplot graph with the matched district and state level data as well on the same graph, so as to compare where the school of interest falls as compared to the district and state. What do I...
  20. Z

    Calculating D from interaction F values

    Hi everyone I am reviewing a study where I need to calculate an effect size of gender differences (Cohen's d). The study looks at the effect of effort on men and women, but do not report the standard deviations for me to calculate d, but do report an repeated measures ANOVA value interaction...