INFERENTIAL STATS- non/parametric tests Flashcards
Statistical tests are classified into two types
Parametric
Non-parametric
Criteria for using a parametic test
-Populations drawn from should be normally distributed.
-Variances of populations should be approximately equal.
-Should have at least interval or ratio data.
-Should be NO extreme scores.
Powerfulness of parametric tests
If there is a difference in populations or a relationship between two variables, these tests are likely to find more info from the data.
Reasons for using NON-PARAMETRIC tests
- When assumptions of parametric test cannot be fulfilled.
- When distributions are not normal.
Types of non-parametric tests
-Mann Whitney U test
-Chi Square
-Binomial sign test
-Wilcoxon signed ranks test
-Correlations Spearman’s Rho
Type of data when using non-parametric test
Do the findings use nominal, ordinal or interval data?
Experimental design when using non-parametric
Independent measures or repeated measures design.
Differences in conditions when using non-parametric
Are you exploring differences in performance, test scores, between two conditions in your experimental study?
What are you looking for when using a non-parametric test
A relationship (correlation) between two co-variables
Observed value
Number produced after various steps and calculations for a statistical test have been carried out.
Critical value
Value taken from a statistical test table, must be reached in order for results to be significant.
Significant
If observed value of U is SMALLER than critical value
Ordinal/ Interval data & Independent measures
Mann Whitney U test
Ordinal/ Interval & Repeated measures
Wilcoxon signed ranks test
Nominal & Independent measures
Chi square
(can also be used to test an association)
Nominal & Repeated measures
Binomial sign test
Exploring relationship between 2 co-variables correlations & ordinal/ interval data
Spearman’s Rho
Checklist for Mann Whitney U test
~ DV produces ORDINAL/INTERVAL type data.
~ Independent measures design.
~ Explores a difference between each condition (levels of IV).
Step 1 Mann Whitney
Place data in rank order from low to high (put both groups together).
Rank should only go up to number of ps in total.
If there are double values ( two same numbers ranked after each other)
Add two together and divide by how many had same score.