Inferential Statistics – Finding the critical values
You will notbe askedhowto workout the inferential tests –butyou mightbe askedto workout
whetherthe testissignificantusingcritical values.
Each test hasa differenttable –youdo not need tolearnthe table butyou doneedto know how to
Spearman’s Rho - correlation
The first inferential test we will look at is a test of correlation – Spearman’s rho. It is used to determine
whether the correlation between two co-variables is significant or not.
Critical values table for Spearman’s Rho
Directional hypothesis – one-tailed
Non-directional= two tailed test
N= means number of participants.
Chi-Square (x2) test – this deals with nominal data i.e. data that is in categories. We use this test
when we have counted how many occurrences there are in each category – called ‘frequency data’.
This test is done slightly differently so take note!
Is a test of difference’. We can look at whether two samples of data are different or not
different from each other i.e. that they are drawn from the same population (the null
hypothesis) or from two different populations. Tests of difference are generally used for
experiments. For example we might conduct an experiment to see if noisy conditions reduce the
effectiveness of revision.
Wilcoxon Test – This is used when pairs of data are related such as a repeated measures
design. Each participant is tested twice and their scores are compared to see if there is any
difference. Matched pairs is also a related design – where there are two groups of participants,
but each participant in one group is matched with a participant in the other group on key
variables, so in a sense it is like testing the same person twice.