Non parametric tests Flashcards
What are meant by non-parametric tests?
Non-parametric tests are tests where there are no assumptions about the distribution
Do non-parametric tests use a random sample?
Yeah baby
Comment of the sensitivity of non-parametric tests to outliers
not sensitive to outliers
Do non parametric tests work with large or small data sets?
Both
What distribution are non-parametric tests useful for?
All
How do non-parametric tests give values to scores?
Rankings
What is the test statistic for non-parametric tests?
the test statistic of non-parametric tests is the difference between the mean ranking or sum ranking.
What is the p-value for non-parametric tests?
the difference between the mean ranking or sum ranking is standardised and the p-value for non-parametric tests is based on this standardisation.
Why are parametric tests preferred over non-parametric tests when possible?
because parametric tests have more power than non-parametric tests and not every parametric test has a non-parametric alternative.
What is the equivalent of the independent samples t test for non parametric? What does it test?
The Wilcoxon rank-sum test, two independent samples
What does the Wilcoxon test use?
It uses the sum of the ranks per group and uses a z-score. The difference in group rank is used.
What test does the same as the Wilcoxon test?
The Mann-Whitney test
What non parametric test is used for two dependent samples?
The Wilcoxon signed-rank test
What does The Wilcoxon signed-rank test use as a test statistic?
It assigned a ‘+’ or ‘-‘ to the difference between two repeated measures. The ranks for the positive group are summed and standardised.
What is the Kruskal-Wallis test used for?
The Kruskal-Wallis test uses more than two independent samples.
What does the Kruskal-Wallis test do?
It subtracts the expected mean ranking from the observed mean ranking and makes use of a Chi-square distribution.
What test utilises more than two dependent samples?
Friedman’s ANOVA
What does Ri denote?
the sum of ranks for each group.
How is the effect size for the Wilcoxon rank-sum test and the Mann-Whitney test calculated?
r= z/ sqrt(n)
When is a Kolmogorov-Smirnov Z test utilised?
This tests whether two groups have been drawn from the same population and has more power than the Mann-Whitney test when the sample sizes are smaller than 25 per group.
When is the Moses Extreme reaction test utilised?
This tests the variability of scores across the two groups and is a non-parametric equivalent of Levene’s test of equal variances.
What does the Wald-Wolfowitz runs test do?
This tests clusters of scores in order to determine whether groups differ.
What should happen if there is no difference in the Wald-Wolfowitz run test?
The ranks should be randomly interspersed if there is no difference.
What does the sign test do?
This does the same as the Wilcoxon-signed rank test but is only based on the direction of the difference in ranks. The magnitude of change is neglected.
