PSY 429 Experimental Psychology

Class Exercise #9

 One-Way Repeated Measures Analysis of Variance

 

 1.What advantages do repeated-measures designs have over an independent-measures design?

2. How does the error term differ for repeated- versus independent-measures ANOVA?

3. A researcher reports an F ratio with df = 3, 36 for a repeated-measures ANOVA. How many treatment conditions were evaluated in this experiment?

4. A researcher conducts a repeated-measures experiment using a sample of n = 12 participants per group to evaluate the differences among three treatment conditions. If the results are examined with an ANOVA, what would be the df values for the F-ratio?

5. To determine the long-term effectiveness of relaxation training on anxiety, a researcher uses a repeated measures design. A random sample of n = 10 subjects is first tested for the severity of anxiety with a standardized test. In addition to this pretest, subjects are tested again 1 week, 1 month, 6 months, and 1 year after treatment. The investigator used ANOVA to evaluate these data, and portions of the results are presented in the following summary table. Fill in the missing values. (Hint: Start with df values)

6. What are the assumptions which should be met if you want to use a repeated-measures ANOVA?

7. The following data were obtained to compare three experimental treatments.

a. If these data were obtained from an independent-measures design, then could you conclude that there is a significant difference among the treatment conditions? Test with alpha set at .05.

b. If these data were obtained from a repeated-measures design, so that each row of scores represents data from a single subject, then could you conclude that there is a significant difference among the treatment conditions? Test with alpha set at .05.

c. Explain the difference in the results of part a and part b, if any.

8. The following data represent idealized results from an experiment comparing two treatments. Notice that the mean for treatment II is 4 points higher than the mean for treatment I. Also notice that this 4-point treatment effect is perfectly consistent for all subjects.

a. Calculate the SS-error for these data

b. Calculate the SS-treatment for these data.

c. Can you explain where the variability appears to come from and why?

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