| Tag | Value |
|---|---|
| file | Inferential_Statistics_eur-inferential_statistics-208-en_eur-inferential_statistics-208-en |
| name | eur-inferential_statistics-208-en |
| section | Inferential Statistics/Effect size/Cohen's d, Reliability/Analysis/Cronbach's alpha |
| type | num |
| solution | 0.63 |
| tolerance | 0 |
| Type | Calculate |
| Program | Calculator |
| Language | English |
| Level | Statistical Literacy |
A PhD student at the institute of Psychology investigates the effect of gender in video modelling on the accuracy on a later task in which the participants have to perform a similar task as was explained in the video by a male or female model. From a meta study he learned that he may expect a main effect for gender: both male and female students learn more from male video models than from female video models. The effect-size in this meta-study was .80. Based on this effect-size the PhD makes a power calculation and decides that he needs 18 participants in each of the two conditions.
Below you see the descriptive statistics the PhD student got from SPSS.
| Group | Mean | SD | n |
|---|---|---|---|
| Male model | 20 | 1.8 | 18 |
| Female model | 20 | 1.7 | 18 |
The reliability of the accuracy scores of the PhD student turned out to be .64. Calculate the effect-size of the data using these descriptive data from the study of the PhD student. Round to 2 decimals.
The formula for the effect-size is: . Since both groups consist of 18 people the pooled standard deviation is simply the average of the two standard deviations. The pooled standard deviation is . So the effect-size (Cohen’s d) is