Lecture 9

Question 1

what is interaction

Answer 1

the effect of 1 IV depends on the effect of the other variable

eg:

• lifting weights can improve strength
• taking steroids can improve strength
• effect of lifting weights on strength could be AMPLIFIED with steroid consumption

Question 2

what is a marginal mean

Answer 2

average scores from a group or subgroup in an experiment

Question 3

what is the characteristics of interaction effect graph

Answer 3

should always display crossing over of lines

Question 4

“if the lines in interaction graph are not parallel, this indicates interaction” true of false

Answer 4

false. interaction effect can only be decomposed by looking at the cell means for each components

Question 5

2 approaches to linear contrasts approach?

Answer 5

main effect contrasts and interaction contrasts

Question 6

what is main effect contrasts approach

Answer 6

compare the cell means of the 2-way table to investigate contrasts of each factor

Question 7

what is interaction contrasts approach

Answer 7

compare the cell means of the 2-way table using the CROSS PRODUCT of contrast weights from the linear comparisons for main effect linear contrasts

Question 8

‘order’ default in coding of contrast differ in terms of whether it is main effect contrast or interaction contrast. what is the difference?

Answer 8

order default for main effect contrast = 0

order default for interaction contrast = 1