A developmental psychologist gives 4th-, 6th-, and 8th-grade children two types of critical thinking tests. There are 28 children tested at each grade level; 14 received one form (A or B) of the test. The dependent measure is the percentage correct on the tests. The mean percentage correct for the children at each grade level and for the two tests is as follows:

A. Draw a graph showing the mean results for this experiment. Based on your examination of the graph, would you suspect a statistically significant interaction effect between the variables? Explain why or why not.

B. Which effects were statistically significant?

Describe verbally each of the statistically significant effects.

C. What are the eta-squared values for the main effects of grade and test?

D. What further analyses could you do to determine the source of the interaction effect?

E. What is the simple main effect of test for each level of grade?

F. Calculate confidence intervals for the six means in the experiment, and draw them around the means in your graph of these results.

Transcribed Image Text:

Test Form A Form B 4th 38.14 52.29 Source Grade Test Grade X Test Error Here is the ANOVA Summary Table for this experiment: Sum of Squares 6th 63.64 68.64 Mean df Square F 17698.95 2 8849.48 96.72 920.05 1 920.05 10.06 658.67 2 329.33 3.60 7136.29 78 91.49 8th 80.21 80.93 Р .000 .002 .032