Question: Recent research indicates that the effectiveness of anti-depressant medication is directly related to the severity of the depression (Khan, Brodhead, Kolts, & Brown, 2005). Based on pre-treatment depression scores, patients were divided into four groups based on their level of depression. After receiving the antidepressant medication, depression scores were measured again and the amount of improvement was recorded for each patient. The following data are similar to the results of the study.

a. Do the data indicate significant differences among the four levels of severity? Test with α = .05.

b. Compute η2, the percentage of variance explained by the group differences.

_ _________________________________________________________

Low High Moderately

Moderate Moderate Severe Severe_______________

0 2 4 3 EX2=204

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M=1 M=2 M=4 M=5

T=4 T=8 T=16 T=20

SS=4 SS=2 SS=8 SS=6