Question

A researcher conducts an experiment to compare the effectiveness of different therapies for depression. Participants diagnosed with depression are randomly assigned to one of four groups: Control (no therapy provided), antidepressant medication (SSRI), cognitive-behavioral therapy (CBT), or a combination of medication and cognitive-behavioral therapy (SSRI+CBT). The DV is depression severity after 4 weeks, with higher scores indicating the presence of more depressive symptoms.

SSRI	CBT	SSRI+CBT	Control
11	7	9	12
5	9	6	7
9	6	7	11
7	11	9	9
6	7	5	6
9	6	8	8
11	9	6	11
10	8	4	10
8	7	8	12
9	9	9	9

Is there a statistically significant difference between the groups? With α = .05, perform a oneway between groups ANOVA to find out.

a. Perform the ANOVA in Excel by creating your own formulas and with the FDIST function to determine p. Create your own full summary table.

b. Compute the effect size (eta squared).

c. Create either a bar graph comparing the means of the four groups (including standard error bars) or a box-plot display comparing the four groups.

d. Insert a textbox reporting your statistical and research conclusion.

Answer 1

a. Perform the ANOVA in Excel by creating your own formulas and with the FDIST function to determine p. Create your own full summary table.

b. Compute the effect size (eta squared).

c. Create a box-plot display comparing the four groups.

d. Insert a textbox reporting your statistical and research conclusion.

We see that the pvalue is less than 0.05, hence we reject the null hypothesis and conclude that there a statistically significant difference between the groups