A psychologist is interested in whether a certain herb might lower stress levels in people. Twelve college students from the freshmen class are randomly sampled for an experiment. The experiment has two conditions which are given on different days. In condition 1, the students are given the herb for a few days. After this they are then given a test which measures their stress levels. The higher the score, the higher the stress. In condition 2, the same students are given an inactive substance, only they think it is another herb. The following scores are obtained.
|
| Herb | Placebo |
| 6 | 4 | |
| 9 | 2 | |
| 4 | 3 | |
| 1 | 4 | |
| 10 | 5 | |
| 2 | 2 | |
| 2 | 4 | |
| 4 | 3 | |
| 5 | 7 | |
| 4 | 9 | |
| Mean | 4.7 | 4.3 |
| SD | 2.945807 | 2.213594 |
- What are the independent and dependent variables? Label each (1 points).
- Determine the null hypothesis and the alternative hypotheses. Label each (2 points).
- What test should you use to determine if the herb lowers stress levels? What information tells you this (1 point)?
- Calculate the statistic. Should we accept or reject the null hypothesis (1 point)?
- Report your results in APA format, that is include “t (df) = _________, p < / p > __________” at the end of your sentence (1 point).
The psychologist is not sure if his results are due to the time of year. The first study was done the spring. He ran the same study in the fall with another group of students to see if he obtained the same change in stress levels. The following changes in stress level were found during the two classes. Was there a higher change in stress levels in the fall compared to the spring?
| Change in Stress | |
| Spring Class | Fall Class |
| 2 | 3 |
| 7 | 4 |
| 1 | 3 |
| -3 | 9 |
| 5 | 5 |
| 0 | 3 |
| -2 | -1 |
| 1 | 6 |
| -2 | 4 |
| -5 | 2 |
- Determine the null hypothesis and the alternative hypotheses. Label each (2 point).
- What test should you use to determine if time of year effects the outcome? What information tells you this (1 point)?
- Calculate the statistic. Report your results in APA format, that is include “t (df) = _________, p < / p > __________” at the end of your sentence (1 point).
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