A researcher conducted an experiment on the effects of a new “drug” depression. The researcher had a control group, and an experimental group that received nothing, a placebo group, and an experimental group that received the “drug.” A depression inventory that provided a measure of depression on a 50 point scale was used (50 indicates that an individual is very high on the depression variable). The ANOVA summary table appears next, along with the mean depression score for each condition.
Source df SS MS F
Between groups 1,202.313
Within groups 2,118.00
“Drug” Condition Mean n
Minimal 36.26 15
Moderate 33.33 15
High 24.13 15
a) Complete the ANOVA summary table.
b) Is F obt significant at α = .05; at α =.01?
c) Perform post hoc comparisons if necessary.
d) What conclusions can be drawn from the F-ratio and the post hoc comparisons?
e) What is the effect size, and what does this mean?
f) Graph the means.