Practice Problems: t-tests

Researchers want to examine the effect of perceived control on health complaints of geriatric patients in a long-term care facility. Thirty patients are randomly selected to participate in the study. Half are given a plant to care for and half are given a plant but the care is conducted by the staff. Number of health complaints are recorded for each patient over the following seven days. Compute the appropriate t-test for the data provided below.

1. What is your computed answer? t_obs = 3.691

2. What would be the null hypothesis in this study? Control over a plant will have no impact on the number of health complaints. Whether one has control over the care of a plant or not, the number of health complaints will be the same.

3. What would be the alternate hypothesis? The group of individuals who have control over a plant will have either fewer or more health complaints as a group than the group that does not have control over the plants.

4. What probability level did you choose and why? .05 Again, I would like to avoid a Type II error. I would like to be able to demonstrate if the plants have any impact on reducing health complaints.

5. What are your degrees of freedom? N + N - 2 = 28

6. Is there a significant difference between the two groups? Yes, the group that had control over caring for the plants had significantly fewer health complaints. The t_obs was not only in the tail for the .05 level but the .01 level as well.

7. Interpret your answer. Patients with control over a plant had significantly fewer health complaints than patients with no control over the care of the plant (t = 3.691, p < .01)

8. If you have made an error, would it be a Type I or a Type II error? Explain your answer. There is a 1 percent chance that I have made a Type I error. It may be that having control over a plant really has no impact on the number of health complaints of geriatric patients in a long-term care facility.