A researcher uses a single-factor ANCOVA to analyze a pretest-posttest design. The between-groups IV has three levels. There is a significant F value. The researcher should:
A) Use multiple t tests to interpret the results
B) Use a Tukey HSD post hoc test to interpret the results
C) Use simple main effects analysis to interpret the interaction
D) Graph the pretest and posttest means for comparison

Question

Quizplus · Accepted Answer

Since there is a significant F value, indicating that at least one of the groups differs significantly from the others, a post hoc test is necessary to determine which group(s) differ significantly from the others. The Tukey HSD test is appropriate for this type of design, as it controls for the experiment-wise error rate. Multiple t-tests would not be appropriate, as they would inflate the experiment-wise error rate. Simple main effects analysis is used to explore the effect of one factor at a specific level of another factor, and is not appropriate in this situation. Graphing the means would be helpful for visualization, but does not provide a statistical test of significance.

A Researcher Uses a Single-Factor ANCOVA to Analyze a Pretest-Posttest