Non-Parametric Methods Flashcards
What are the non-parametric methods tests?
Mann-Whitney U test
Wilcoxon signed rank test
Spearman’s rank correlation coefficient
When are non-parametric methods used?
When the assumptions for the parametric methods do not hold
What are non-parametric methods based on?
Most are based on ranking the observations
E.G Arranging the observations in increasing order and assigning ranks.
They can also be applied to ordinal scale variable
What are the disadvantages of non-parametric methods?
i) They have less power than there counter part of the relevant assumptions hold
ii) they focus on deriving a P value rather than obtaining a confidence interval
iii) They are less flexible - they cannot be subsumed into more complex forms of analysis
What is the non-parametric counterpart to the independent samples t-test
Mann-Whitney U test
What is the non-parametric counterpart to the paired samples t-test?
Wilcoxon Signed Rank test
What is the non-parametric counterpart to the Pearson’s correlation coefficient?
Spearman’s Rank correlation coefficient
When is the Mann-Whitney U test used?
To compare two independent samples when the outcome is interval scale but assumptions for t-test are not satisfied or when outcome is ordinal
When is the Wilcoxon Signed-Rank test used?
To compare two paired samples when the outcome is interval scale but assumptions for the paired samples t-test is not satisfied or when the outcome is ordinal
What are correlation coefficients?
Between two variables, is the measure of the degree of linear association between the variables on a scale.
-1 = Perfectly inverse relationship
0 = Indicates the two variables are independent
+1 = Perfectly linear relationship
When is Spearman’s Rank Correlation used?
To measure the degree of association between two interval scale variables but the assumptions for Pearson correlation coefficient are not met or when at least one of variables is ordinal
