Question

An investigator conducts a study to examine the benefits of psychotherapy for individuals with depression. Specifically, the investigator predicts that depressed individuals who receive psychotherapy in addition to drug therapy for depression will display significantly lower levels of depression than persons with a diagnosis of depression who receive only drug therapy. The investigator assigns 10 subjects to each of the two conditions stated above. After three months the investigator measures depression using a scale in which higher scores reflect higher levels of depression.

1. Write the null and alternative hypotheses for testing the investigator’s prediction.

2.Please use SPSS using independent t-test to test the null hypothesis stated above and attach the output herewith.

3. State the conclusion the investigator is entitled to draw.

Psychotherapy plus drug therapy group: 23, 19, 16, 18, 15, 22, 16, 18, 19, 20

Drug therapy only: 24, 27, 26, 28, 29, 24, 26, 25, 22, 28

Answer 1

Let mu1 and mu2 be the means of Psychotherapy plus drug therapy group and drug therapy group.

1)

To test H0 : mu1 =mu2

Vs

H1 : mu1 <mu2

B) we have used SPSS then the output of two sample t test is

Test statistic T=-6.8139

And p-value =0.0000

C)

Since the p-value <0.05 we can say that the Psychotherapy plus drug therapy has significantly lower the depression than the only drug therapy at 95% confidence.

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