Statistics T-Test Worksheet

A social worker measured clients' rates of depression using the Beck Depression Scale

1-10_____These ups and downs are considered normal

11-16____ Mild mood disturbance

17-20____Borderline clinical depression

21-30____Moderate depression

31-40____Severe depression

over 40___Extreme depression

The social worker took an initial baseline score, then again after 6 months of therapy, and then again after 12 months.

Baseline 6 Months 12 Months

41 30 15

32 22 16

60 50 48

54 50 37

52 50 41

36 30 10

33 21 15

19 17 22

34 30 21

44 36 11

Mean = Mean = Mean =

S = S = S =

S² = S² = S² =

1. Decide how to compare your data.Which columns will you compare.What is your computed answer?

2. What would be the null hypothesis in this study?

3. What would be the alternate hypothesis?

4. What probability level did you choose and why?

5. Is there a significant difference between the two groups?

6. Interpret your answer.Is therapy effective for this sample?

7. Describe the average scores of depression at baseline, 6 months, and 12 months of therapy.

8. If you have made an error, would it be a Type I or a Type II error? Explain your answer