Practice Problems: ANOVA A research study was conducted to examine the clinical efficacy of a new antidepressant. Depressed patients were randomly assigned to one of three groups: a placebo group, a group that received a low dose of the drug, and a group that received a moderate dose of the drug. After four weeks of treatment, the patients completed the Beck Depression Inventory. The higher the score, the more depressed the patient. The data are presented below. Compute the appropriate test. Placebo Low Dose Moderate Dose 38 22 14 47 19 26 39 8 11 25 23 18 42 31 5 What is your computed answer? What would be the null hypothesis in this study? What would be the alternate hypothesis? What probability level did you choose and why? What is your Fcrit? Is there a significant difference between the groups? If there is a significant difference, where specifically are the differences? Interpret your answer.
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
Practice Problems: ANOVA
A research study was conducted to examine the clinical efficacy of a new antidepressant. Depressed patients were randomly assigned to one of three groups: a placebo group, a group that received a low dose of the drug, and a group that received a moderate dose of the drug. After four weeks of treatment, the patients completed the Beck Depression Inventory. The higher the score, the more depressed the patient. The data are presented below. Compute the appropriate test.
| Placebo | Low Dose | Moderate Dose |
| 38 | 22 | 14 |
| 47 | 19 | 26 |
| 39 | 8 | 11 |
| 25 | 23 | 18 |
| 42 | 31 | 5 |
- What is your computed answer?
- What would be the null hypothesis in this study?
- What would be the alternate hypothesis?
- What probability level did you choose and why?
- What is your Fcrit?
- Is there a significant difference between the groups?
- If there is a significant difference, where specifically are the differences?
- Interpret your answer.
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