A researcher wants to test the effectiveness of an experimental treatment for de

Question

A researcher wants to test the effectiveness of an experimental treatment for depression which involves exercise and classical music. He randomly selects n = 50 patients taking depression medication from several clinics and invites them to his lab where he assesses their levels of depression with the Beck Depression Inventory (rated 0-63, with higher scores indicating more severe levels of depression). He finds that their mean depression score is M = 24.3 with a standard deviation of s = 14.47. He then has them come to the lab four times a week to exercise on an elliptical for 30 minutes while listening to Johann Sebastian Bach over the course of one month. After the month, the researcher reassesses the patients with the Beck Depression Inventory and finds that their mean depression score is M = 17.08 with a standard deviation of s = 20.02. The researcher conducts a repeated-measures t-test to see if results suggest there is a significant (alpha = .05) decrease in depression symptoms (i.e., Beck Depression Inventory scores) after this exercise and Classical music treatment. The researcher computes a value of t = -10.22 for the sample data (Step 3). What is the correct decision and conclusion (Step 4) for the hypothesis test?

Explanation / Answer

Since n is large(n>30), we assume tN(0,1).

Critical value is, z.05 = 1.64

t* = -10.22 < -1.64

Reject H0.

Hence the decrease in symptoms of depression after the exercise and classical music treatment is significant.

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