Lecture 7C: Two-way ANOVA

Question 1

What is the objective of two-way ANOVA?

Answer 1

To compare the means of ≥3 unrelated groups with two IVs

• e.g. Comparing IQ scores of male and female children from three different ethnicities

Question 2

What are the two effects determined by two-way ANOVA?

Answer 2

Main effects

• effect of each IV
• e.g. no difference in IQ scores between 3
  ethnicities + no difference in IQ scores between males and females

Interaction effect
* interaction between the two IVs
* e.g. the gender difference in IQ scores is not ethnicity dependent

Question 3

In a two-way ANOVA design, what does J represent?

Answer 3

The number of levels for independent variable 1 (rows)

Question 4

In a two-way ANOVA design, what does K represent?

Answer 4

The number of levels for independent variable 2 (columns)

Question 5

What does a two-way ANOVA generate to assess effects?

Answer 5

F-ratios

Question 6

What statistical test is used for post-hoc analysis in a two-way ANOVA?

Answer 6

Tukey HSD

Question 7

What does the adjusted R Squared value indicate in the two-way ANOVA results?

Answer 7

The proportion of variance explained by the model

Question 8

What is the primary purpose of running descriptive statistics in a two-way ANOVA?

Answer 8

To summarize the means and standard deviations for each group