Non parametric tests

Question 1

What are meant by non-parametric tests?

Answer 1

Non-parametric tests are tests where there are no assumptions about the distribution

Question 2

Do non-parametric tests use a random sample?

Answer 2

Yeah baby

Question 3

Comment of the sensitivity of non-parametric tests to outliers

Answer 3

not sensitive to outliers

Question 4

Do non parametric tests work with large or small data sets?

Answer 4

Both

Question 5

What distribution are non-parametric tests useful for?

Answer 5

All

Question 6

How do non-parametric tests give values to scores?

Answer 6

Rankings

Question 7

What is the test statistic for non-parametric tests?

Answer 7

the test statistic of non-parametric tests is the difference between the mean ranking or sum ranking.

Question 8

What is the p-value for non-parametric tests?

Answer 8

the difference between the mean ranking or sum ranking is standardised and the p-value for non-parametric tests is based on this standardisation.

Question 9

Why are parametric tests preferred over non-parametric tests when possible?

Answer 9

because parametric tests have more power than non-parametric tests and not every parametric test has a non-parametric alternative.

Question 10

What is the equivalent of the independent samples t test for non parametric? What does it test?

Answer 10

The Wilcoxon rank-sum test, two independent samples

Question 11

What does the Wilcoxon test use?

Answer 11

It uses the sum of the ranks per group and uses a z-score. The difference in group rank is used.

Question 12

What test does the same as the Wilcoxon test?

Answer 12

The Mann-Whitney test

Question 13

What non parametric test is used for two dependent samples?

Answer 13

The Wilcoxon signed-rank test

Question 14

What does The Wilcoxon signed-rank test use as a test statistic?

Answer 14

It assigned a ‘+’ or ‘-‘ to the difference between two repeated measures. The ranks for the positive group are summed and standardised.

Question 15

What is the Kruskal-Wallis test used for?

Answer 15

The Kruskal-Wallis test uses more than two independent samples.

Question 16

What does the Kruskal-Wallis test do?

Answer 16

It subtracts the expected mean ranking from the observed mean ranking and makes use of a Chi-square distribution.

Question 17

What test utilises more than two dependent samples?

Answer 17

Friedman’s ANOVA

Question 18

What does Ri denote?

Answer 18

the sum of ranks for each group.

Question 19

How is the effect size for the Wilcoxon rank-sum test and the Mann-Whitney test calculated?

Answer 19

r= z/ sqrt(n)

Question 20

When is a Kolmogorov-Smirnov Z test utilised?

Answer 20

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.

Question 21

When is the Moses Extreme reaction test utilised?

Answer 21

This tests the variability of scores across the two groups and is a non-parametric equivalent of Levene’s test of equal variances.

Question 22

What does the Wald-Wolfowitz runs test do?

Answer 22

This tests clusters of scores in order to determine whether groups differ.

Question 23

What should happen if there is no difference in the Wald-Wolfowitz run test?

Answer 23

The ranks should be randomly interspersed if there is no difference.

Question 24

What does the sign test do?

Answer 24

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.

Question 25

Comment on the power of the sign test

Answer 25

This test lacks power unless the sample size is very small.

Question 26

What does McNemar’s test compare?

Answer 26

This test compares the number of people who changed their response to one direction to those who changed it in the opposite direction

Question 27

What data does McNemar’s test use?

Answer 27

uses nominal, rather than ordinal data.

Question 28

When is McNemar’s test useful?

Answer 28

It is useful when looking for changes in people’s scores.

Question 29

Name an extension to McNemar’s test and what it is similar to

Answer 29

Marginal homogeneity is an extension of McNemar’s test and is similar to the Wilcoxon test.

Question 30

Name the non-parametric equivelant of an ANOVA to compare two groups and comment on its power

Answer 30

Friedman’s 2-way ANOVA by ranks (k samples) is the non-parametric equivalent of an ANOVA to compare two groups but it has low power compared to the Wilcoxon signed-rank test.

Question 31

What does the median test test?

Answer 31

This tests whether the samples are drawn from a population with the same median.

Question 32

What does the Jonckheere-Terstra test for?

Answer 32

an ordered pattern of the medians of the group

Question 33

How does the Jonckheere-Terstra test differ from the Kruskal-Wallis test

Answer 33

It does the same as the Kruskal- Wallis test but incorporates the order of the groups.

Question 34

When is the Jonckheere-Terpstra useful?

Answer 34

It is useful to test for trends in the data and should be used when a meaningful order of medians is expected.

Question 35

What does Kendall’s W test?

Answer 35

the agreement between raters and ranges between 0 and 1.

Question 36

What does Cochran’s Q test do?

Answer 36

This is Friedman’s test on dichotomous data.