Week 5: Multiple Groups Designs & Analysis of Variance (ANOVA)

Question 1

Analysis of Variance (ANOVA)

Answer 1

Statistical test used to analyse difference between the means of two (or more) groups

Also called an omnibus test

ANOVA quantified sources of variability in data to ascertain if sampling error alone can account for differences in scores between groups.

ANOVA does this my looking at ratio of variability between groups, compared to variability within groups.

Question 2

F ratio

Answer 2

Used to evaluate whether the between-groups variability (effect of IV) is greater than within-group variability (error)

Used to compare multiple group means.

F = Between Group Variance/Within Group Variance

BG represents IV effect
WG represents sampling error

A larger F ratio indicates higher significance.
F ratio likely to be larger when: the difference between groups large, thus increasing the BG and/or the difference within group is small, thus decreasing our WG

Question 3

Between-Group Variability (BG)

Answer 3

Variance between group means is determined by looking at how group means vary around the grand mean.
BG variability is caused by sampling error and the effect of the IV

Question 4

Within-Group Variability (WG)

Answer 4

WG variability is calculated for each group separately.

WG variability is caused by sampling error.