12. Comparison of Several Means 1

Question 1

What do you use with 2 samples?

Answer 1

t-test

Question 2

What is ANOVA?

Answer 2

analysis of variance

Question 3

Why use an ANOVA instead of multiple t-tests?

Answer 3

when you run multiple t-tests, get an inflated familywise (type I error) rate

Question 4

What does an ANOVA do?

Answer 4

tests whether 3+ means are the same or not

Question 5

What type of test is an ANOVA?

Answer 5

omnibus test

Question 6

What is an omnibus test?

Answer 6

• tests for overall experimental effect

- doesn’t provide info regarding which groups were affected

Question 7

f-stat equation

Answer 7

f-stat = model/error

Question 8

What does the f-stat tell us?

Answer 8

• only that the experimental manipulation had some effect

- doesn’t tell specifically what it was

Question 9

ANOVA partitions variance into two categories

Answer 9

• systematic

- unsystematic

Question 10

SS_T

Answer 10

• total sum of squares

- total amount of variation within a data set

Question 11

SS_M

Answer 11

• model sum of squares

- amount of systematic variation (explained by the model)

Question 12

SS_R

Answer 12

• residual sum of squares

- amount of unsystematic variation (not explained by the model)

Question 13

MS_M

Answer 13

• mean squares model

- SS_M ÷ df_M

Question 14

MS_R

Answer 14

• mean squares residual

- SS_R ÷ df_R

Question 15

f-stat equation

Answer 15

MS_M ÷ MS_R

Question 16

df_M

Answer 16

one less than the number of groups

k-1

Question 17

df_R

Answer 17

total degrees of freedom - df_M

N-K (total sample size - number of groups)

Question 18

What do you do once you calculate the f-stat?

Answer 18

compare to critical value with the same df in the appendix

Question 19

If the f-stat is more than the critical value:

Answer 19

• difference between means due to more than chance

- significant difference

Question 20

If the f-stat is less than the critical value:

Answer 20

• difference between means due to only chance

- not a significant value

Question 21

types of ANOVAs

Answer 21

• one-way independent
• factorial ANOVA
• ANCOVA

Question 22

IVs for a one-way ANOVA

Answer 22

1 IV with between group differences

Question 23

IVs for a factorial ANOVA

Answer 23

2+ IVs

Question 24

What is an ANCOVA?

Answer 24

ANOVA with an addition of a covariate