L14 - FRIEDMANS ANOVA Flashcards
(22 cards)
What type of test is Friedman’s ANOVA?
A non-parametric test using ordinal level data (ranks)
When is Friedman’s ANOVA used?
For repeated measures designs with 3 or more conditions on the same participants
What is the non-parametric equivalent of the repeated measures t-test for 2 groups?
Wilcoxon Signed-Rank Test (WST).
What is Friedman’s ANOVA an alternative to?
Repeated measures one-way ANOVA when assumptions of parametric tests are violated.
What is a key assumption of repeated measures ANOVA regarding the dependent variable?
The dependent variable needs to be normally distributed.
What corrections can software like JASP provide when the sphericity assumption is violated in repeated measures ANOVA?
Greenhouse-Geisser and Huynh-Feldt corrections adjust degrees of freedom to reduce Type 1 error.
What are three options if the assumption of sphericity is violated?
- Continue with one-way ANOVA (it may be robust enough)
- Perform data transformations (e.g., log, square-root)
- Use a non-parametric test (e.g., Friedman’s ANOVA)
: Describe the example with the Year 5 teacher using Friedman’s ANOVA.
The teacher tested pupils’ multiplication performance over 3 months (Sept, Oct, Nov), with 6 tests each month, to see if performance improved.
If Participant 8 scored 72 in month 1, 74 in month 2, and 55 in month 3, what are the ranks?
Month 3 = 1 (lowest score), Month 1 = 2 (2nd highest), Month 2 = 3 (highest).
How can you check if data is normally distributed?
Eyeball a histogram for a bell-shaped curve (subjective)
What objective measures can help assess normality?
Skewness, kurtosis, and tests for deviation from a normal distribution.
What does a non-significant Shapiro-Wilk result mean?
The sample distribution likely does not differ from a normal distribution (i.e., data is likely normal).
Why should you be cautious interpreting Shapiro-Wilk results with large samples?
: Large samples can yield significant results for minor deviations from normality.
What should you do alongside Shapiro-Wilk to decide on the right test?
Plot the data and visually inspect it before deciding
What is sphericity in repeated measures ANOVA?
The variances of the differences between all conditions should be roughly equal
How do you test for sphericity?
Using Mauchly’s Test of Sphericity.
What if Mauchly’s test is significant?
Apply corrections like Greenhouse-Geisser or Huynh-Feldt, or use Friedman’s ANOVA.
Which software automatically tests for sphericity?
JASP
In statistical analysis, when should you use the Mann-Whitney U test?
A. When comparing means of two independent groups with normally distributed data.
B. When comparing the ranked scores of two independent groups with non-normally
distributed data.
C. When dealing with paired observations and a small sample size.
D. When analyzing the variance between multiple groups.
B
What is the non-parametric alternative to a repeated measures t-test?
A. Mann-Whitney U
B. Friedman’s ANOVA
C. Kruskal Wallis
D. Wilcoxan-signed ranks
D
When would a Kruskal Wallis test be used?
A. When you have one IV with three levels and a between-subjects design
B. When you have one IV with two levels and a between-subjects design
C. When you have one IV with three levels and a within-subjects design
D. When you have one IV with two levels and a within-subjects design
A
When would you report Friedman ANOVA results?
A. H (2) = 7.6, p = .022, η2 = .382
B. ² (2) = 7.6, p = .022, Kendall’s ω2 = .382
C. U = 7.6, p = .022, r = .382
D. T (12) = 9, p = .01, r = .77
B
