Lecture 6

Question 1

Which test compares 2 means and only has 1 IV?

Answer 1

t-test

Question 2

Which test compares 3+ means and can be used when you have manipulated more than one IV?

Answer 2

ANOVA or “factorial!”

Question 3

When I use a lot of t-tests to compare several means, this inflates the ______

Answer 3

alpha
OR
Type 1 Error Rate

Question 4

What is another name for ANOVA test?

Answer 4

Omnibus test

Question 5

What does ANOVA do?

Answer 5

• tests for overall difference
• tells us that means are different
• doesn’t tell us exactly which means differ

Question 6

What is an “overall test” that tests a number of different comparisons at once?

Answer 6

Omnibus

Question 7

What question does ANOVA test?

Answer 7

Is there a difference somewhere?

Question 8

What is the SS?

Answer 8

sum of squares or total amount of variance

Question 9

What is the MS equation?

Answer 9

MS = Mean Square
MS = SS/df

Question 10

F = ?

Answer 10

MS (between) / MS (within)

Question 11

Why do we use follow-up tests?

Answer 11

Omnibus tells us that there IS a difference among the means, not WHERE

Follow up tests tell us WHERE the group differences lie

Question 12

What is a planned contrast (follow up) test?

Answer 12

• Has statistical advantage
• Type of contrasts are limited
• Needs to be planned a priori

Question 13

What is a post hoc comparison (follow up) test?

Answer 13

• MOST common
• not planned
• compares ALL pairs of means

Question 14

What is a pairwise test?

Answer 14

Typically after global test & implies ONLY 2 means

Question 15

What is simple effects?

Answer 15

run this after global test & significant interaction

Question 16

Which tests can we use if there are only (1) small deviations from normality, (2) sample sizes in each cell are equal, and (3) variances are homogenous?

Answer 16

Bonferroni & Tukey

Question 17

Which tests are conservative and controls for type 1 error?

Answer 17

Bonferroni & Tukey

Question 18

Bonferroni has more power than Tukey if ______

Answer 18

number of comparisons are small

Question 19

Tukey has more power than Bonferroni if _____

Answer 19

the number of comparisons are large

and more power than Dunn and Scheffe

Question 20

Which test do you use if variances are not homogenous?

Answer 20

Games-Howell

Question 21

What is the Games-Howell?

Answer 21

Powerful but can be liberal when sample sizes are small. Accurate with unequal sample sizes

Question 22

What is the Kruskal-Wallis Test?

Answer 22

The non-parametric equivalent to an independent one-way ANOVA

• select if your data doesn’t meet assumptions
• Mann-Whitney U tests

Question 23

What is the HOV assumption equivalent in ANOVA called?

Answer 23

Sphericity

Question 24

What is the sphericity assumption?

Answer 24

The variances of the differences between all possible pairs of groups are equal

Question 25

What is the test for sphericity called?

Answer 25

Mauchley’s test

Question 26

When you have F(2,10) = 12.5, what does the 1st number mean? what does the 2nd number mean?

Answer 26

1st number: # of groups 2nd number: # of participants per group

Question 27

What is Friedman's ANOVA?

Answer 27

non-parametric equivalent of RM - one-way ANOVA

Question 28

What is the difference between a two-way independent ANOVA vs. a factorial ANOVA analysis?

Answer 28

2-way independent ANOVA has 2 IV's factorial ANOVA has 1 IV

Question 29

What does "interaction" look for?

Answer 29

Interesting relationships between the independent variables

Question 30

T/F: If the interaction is significant, don't worry about the main effects.

Answer 30

True

Question 31

If the interaction lines are parallel, is it significant?

Answer 31

No

Question 32

When the interaction is significant, you can run ___ ____

Answer 32

simple effects

Question 33

If **main effect(s)** is significant and interaction is NOT significant, you should run ________

Answer 33

Follow-up main effect pairwise comparisons & report. Adjust alpha level! Note: if only 2 levels for main effect, no follow-up testing needed

Question 34

If **main effect(s)** is significant AND interaction is significant, you should run _____

Answer 34

Simple effects and "forget about" main effects. Adjust alpha level!

Question 35

When do you run simple effects?

Answer 35

If you have a significant interaction!

Question 36

If I am studying self-perceived preparedness in Dental students. I have 3 independent variables and 1 dependent variable. What type of test should I run?

Answer 36

Split/Mixed 3-way Factorial ANOVA

Question 37

If I am studying self-perceived preparedness in Dental students. I have 3 independent variables and 1 dependent variable. How many main effects? How many 2-way interactions? How many 3-way interactions?

Answer 37

3 Main Effects 3 2-way Interactions 1 3-way Interaction

Question 38

What is a covariate?

Answer 38

A variable that is complementary or related to the dependent variable; **extraneous** variable

Question 39

When would you test for covariates?

Answer 39

Test differences between group means when we know that an extraneous/confounding variable can **affect the outcome variable**

Question 40

WHY would you test for covariates?

Answer 40

To strengthen your analysis More likely to find significance if you can identify the covariate and measure it beforehand

Question 41

What is ANCOVA?

Answer 41

analysis of covariance *run analysis on the adjusted means*

Question 42

What is MANOVA?

Answer 42

Multivariate analysis of variance

Question 43

When do you use MANOVA?

Answer 43

To test for differences between groups when we have **several DVs**

Question 44

Why is MANOVA better than multiple ANOVAs?

Answer 44

* controls familywise error rate (Type 1 error) Note: takes into account relationship between the DVs; more powerful than separate ANOVAs **DVs are mathematically combined into aggregate turning it into one variable for the global**

Question 45

What's the next step after a significant Global MANOVA?

Answer 45

DFA (Discriminant function analysis)

Question 46

What is DFA (Discriminant function analysis) used for?

Answer 46

Used to determine which of the DVs are best at discriminating the groups