Twenty sets of depressedtwins are obtained for a study on the effects of a new a

Question

Twenty sets of depressedtwins are obtained for a study on the effects of a new antidepressant. Ineach twin set, one twin is assigned to receive the drug and the other is designed to receive the placebo. Three months later, depression levels are measured on a scale from 1 (not at all depressed) to 7 (very depressed) The following data were obtained GROUP 1-Received drug GROUP 2- Received placebo Variable Depression level GROUPN Mean SD GROUP 110 GROUP 2 10 321 5.77 1035 1.772 | ,-5785 dr-9 p-0017 Cohaud-.88 1. What is the independent vanable? 2. Whatis the dependent variable? 3. Whatkind of research design was used? The independent is the medication. The dependent variable is the level of depression as measured on the scale. The research design used is the between subjects design, it involves the use of two participant groups 4. What kind of statistical analysis was used? The t-test was used in the case. The study compared the differences in the means ofthe two experimental conditions 5. Is the effect size small, medium, or large? How do youknow? 6. Write an APA-format conclusion Insert Prn

Explanation / Answer

5. In the given study, the effect size ( denoted by Cohen’s d) is very large. According to Cohen, d=0.2 can be considered a 'small' effect size, 0.5 represents a 'medium' effect size and 0.8 a 'large' effect size. This means that if two groups' means don't differ by 0.2 standard deviations or more, the difference is trivial, even if it is statistically signficant.

6.A valid conclusion for the given study according to the APA standard can be:

‘ the present study was carried out in order to explore the effects of a new antidepressant on depressed patients. A sample of depressed twins was used to establish whether the new antidepressant is effective even in cases of genetically predisposed depression. Using ANOVA to find the variability of between subjects design, the study showed that the new antidepressant produced significant difference in the level of depression in the experimental group of twins compared to the control group of twins on placebo. The new range of antidepressant could thus show promising result even in cases of a strong heritability factor in depression. Further research is required in the area using a larger sample of twins and the general population to establish the efficacy of the antidepressants as a popular pharmacological treatment for clinical depression.’

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