Chapter 11 (ANOVA)

Question 1

When do we use ANOVA (analysis of variance)?

Answer 1

When we want to make a comparison between three or more means

Question 2

What does the mean squares represent?

Answer 2

The between group variability and the within group variability.

Between is on top
Within is on bottom

Question 3

When do we do in pairwise comparisons?

Answer 3

When we reject H_o in an ANOVA and want to see which means are different between groups.

Question 4

Why do we do pairwise comparisons?

Answer 4

To be able to see which groups have different means

Question 5

What is the F statistics in an ANOVA?

Answer 5

F = MSTr/MSE (top value in the Mean Squares column divided by the bottom value in the same column)

Question 6

How do you find the treatment degrees of freedom?

Answer 6

k-1,

for k = number of groups

Question 7

What does H_o look like for an ANOVA?

Answer 7

H_o: µ1 = µ2 = … = µk,
where µ1 = mean of group 1,
µ2 = mean of group 2,
etc, etc.

Question 8

What does H_A look like for an ANOVA?

Answer 8

H_A: µ_i ≠ µ_j for some i and j.

Question 9

What do we assume when doing ANOVA?

Answer 9

1) the samples from the k populations are random
2) the observations within each group are approximately normally distributed. (or n for each group is large enough to assume approximate normality of sample means)
3) the underlying k populations all have the same variance.