Spearman’s rho:
Used when –
Hypothesis predicts a correlation
Two sets of data are pairs of scores from one person (independent
measures)
Ordinal (or interval) data
Step one –
Put data into columns then rank data (if some data is the same number, find
average rank of no. of ranks these numbers would have taken up), need two
sets of ranks, one for each column (category/score, A and B)
Step two –
Find difference between ranks for each individual (A-B) to find d
Step three –
Square all d scores (d 2) and then add all these up (d 2), then find number of
participants for N and establish if hypothesis is one-tailed or two-tailed
Step four –
6 Σ d2
Calculate rho using formula: rho=1− 2 to find observed value r
N ( N −1)
Step five –
Use table to find critical value, if observed value is equal to/more than critical
value, we can reject the null hypothesis
Used when –
Hypothesis predicts a correlation
Two sets of data are pairs of scores from one person (independent
measures)
Ordinal (or interval) data
Step one –
Put data into columns then rank data (if some data is the same number, find
average rank of no. of ranks these numbers would have taken up), need two
sets of ranks, one for each column (category/score, A and B)
Step two –
Find difference between ranks for each individual (A-B) to find d
Step three –
Square all d scores (d 2) and then add all these up (d 2), then find number of
participants for N and establish if hypothesis is one-tailed or two-tailed
Step four –
6 Σ d2
Calculate rho using formula: rho=1− 2 to find observed value r
N ( N −1)
Step five –
Use table to find critical value, if observed value is equal to/more than critical
value, we can reject the null hypothesis
