Exam 12: Multiple Comparison Procedures

The same researcher now wants to examine if student scores will increase as the instructional time increases. She randomly assigned 60 students to three classes. Each class spent 4 hours, 5 hours, and 6 hours per day respectively on instruction. Then she compared the average scores of the three classes. Which procedure is the most appropriate for this research question?

In post hoc pairwise comparisons, if procedure A yields wider confidence intervals than procedure B does, which procedure is more powerful?

In an experiment, $\bar{Y}_{1}$ =10, $\bar{Y}_{2}$ =200, and $\bar{Y}_{3}$ =4000. Which pairwise contrast will necessarily be significant?

How many possible pairwise contrasts are there if J = 5?

In a study of different instructional methods, if the researcher is only interested in comparing the scores of the class taught by the traditional method against each of the classes taught by the alternative methods, which procedure should she use?

When a one-factor fixed-effects ANOVA results in a nonsignificant F ratio for J = 4, one should follow-up the ANOVA with which one of the following post-hoc procedures?

In the study described in item 18, the researcher finds out that student scores increase significantly when instructional time increases, so she predicts that scores will be even higher if the instructional time is 12 hours per day. Evaluate the prediction.

Dr Guinea Pigg would like to test if the amount of caffeine intake would affect how well laboratory rats performed on a specific task. He randomly assigned 40 rats to five groups (n = 8). Each rat walked the same maze after drinking caffeinated water. The amount of caffeine the rats took and the number of mistakes they made in walking the maze were recorded in the following table. Dosage 10 20 30 40 50 16 16 2 5 7 5 10 9 8 12 Number of 11 7 11 1 14 mistakes 23 12 13 5 16 18 7 10 8 11 12 4 13 11 9 12 23 9 9 19 19 13 9 9 24 Using the data, conduct a trend analysis to test if there is any linear, quadratic, or cubic trend ( $\alpha$ = .05).

If J = 3, which of the following sets of contrasts is orthogonal?

Which of the following statements about trend analysis is true?

For any pairwise MCP, holding the number of groups and df_with constant, as the $\alpha$ level increases, the critical value will

Applying the Dunn procedure, the per contrast alpha is calculated to be 0.01 for five contrasts. What is the nominal family-wise error rate?

Which one of the following procedures does not assume equal group variances?

After a significant F test, a researcher used the Scheffe' method to test all pairwise contrasts and found that all contrasts are significant. He then repeated MCP with the Tukey method. What would he find?

Which of the following linear combinations of population means is a legitimate contrast?

Which of the following procedures can be used to test complex contrasts?

If 5 orthogonal contrasts can be tested, what is the number of levels of the independent variable?

After a significant F test, two different pairwise comparison procedures were used to detect the differences between 5 group means. Procedure A detected one significant contrast, whereas procedure B showed that all contrasts are significant. Which procedure is more powerful?

In the experiment described in Question 3, if instead of a planned test, Dr Guinea Pigg conducted an omnibus ANOVA F test at $\alpha$ = .05 and found out that there was significant difference between the group means. Suppose the group variances are equal. Use the Tukey method to test all possible pairwise contrasts.

Which of the following is not an assumption of Tukey HSD?