Stats 2 Second Exam

Question 1

2 (or more)-way ANOVA is used when one has…

Answer 1

2 or more fixed categorical IVs and 1 or more continuous random DV

Question 2

2-way ANOVA hopes to find

Answer 2

1. Interactions 2. Main effects

Question 3

“2 way ANOVA” indicates _____ whereas “2 x 2 ANOVA” indicates

Answer 3

1. That we have 2 IVs 2. That we have 2 IVs, each with 2 levels.

Question 4

What does “Factorial design” mean?

Answer 4

More than one IV

Question 5

What is the goal of 2-way ANOVA?

Answer 5

Add second IV that strengthens first IV and reduces E

Question 6

What is an interaction?

Answer 6

Second IV affects the levels of 1st IV differently

Question 7

How can one examine interaction graphically?

Answer 7

1. Parallel lines means there is no interaction
2. Test of interaction is test of parallelism. Not testing if means are significantly different
3. Examination of slope (how regression works)

Question 8

What should one do statistically upon finding a significant interaction?

Answer 8

Do not pursue main effects.

Question 9

What are the 3 hypotheses of 2-way ANOVA?

Answer 9

1. Interaction 2. Main effect A 3. Main effect B

Question 10

What is the effect of adding a 2nd IV on power?

Answer 10

1. Doubles number of participants one needs to have in order to achieve sufficient power
2. Because power is based on cells– the smallest breakout that one will compare

Question 11

What questions does one ask in 2-way ANOVA?

Answer 11

1. Is there a significant effect? 2. Where is it? 3. How big is it?

Question 12

What are assumptions of 2-way ANOVA?

Answer 12

1. n 4:1 ratio
2. N - Normality of error term (not normal distribution of subjects). Error term = that for which is not accounted.
3. I - Independence - participants can be in only 1 cell at a time. Cannot randomly assign to a tx group and then a second tx group.
4. H - Homogeneity - Equivalent variances (SDs) of all cells. Across IVs and also across interactions
5. R - Random

Question 13

What does ATI stand for?

Answer 13

Attribute-Treatment Interaction

Question 14

What is Attribute-Treatment Interaction?

Answer 14

• Uses both experimental and ex post facto methods:
• Treatment-Control = experimental variable
• M/F or SES = organismic variable
• Can manipulate one variable but not the other.

Question 15

How is Attribute-Treatment Interaction conducted?

Answer 15

• Randomly assign to treatment (experimental variable).
• Randomly select from attribute (organismic variable).
• May have control and treatment or multiple treatments
• May have control organismic variable.
• Main objective is to assess interaction.

Question 16

What does it mean when lines of interaction graph cross?

Answer 16

1. There is an interaction effect. 2. Termed “Disordinal Interaction”

Question 17

What does it mean when lines of interaction graph change slope but do not cross?

Answer 17

1. There is an interaction effect. 2. Termed “Ordinal Interaction”

Question 18

What does it mean when lines of interaction graph are parallel?

Answer 18

No interaction

Question 19

Interaction hypothesis is addresses through

Answer 19

Graphing

Question 20

Main effect hypotheses are addressed through

Answer 20

Post-hoc tests (if interaction is not demonstrated)

Question 21

What is included in 2-way ANOVA source table?

Answer 21

• Source SS df MS F
• IV (by name)
• IV 2 (by name)
• Interaction
• Error
• Total