AS/A2 Stats 1 Stats 2

S3 Topic 5: Regression and correlation
Ranking data
One way to measure the correlation between two sets of data is to rank each set in order of size and then compare the rankings.

Data Change these two sets of raw data and then put into correct order. Make two of the pieces of data the same in one row, then check how the ranks are calculated.

X
Y

In order

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Y

Rankings of original data from smallest (1) to biggest (10)

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Y

Summary The correlation between the rows in the final table of rankings can be measured using Spearman's Rank Correlation coefficient. Equal ranks If there are any equal ranks, then each is given the mean average of the ranks that would have been allocated, ie, if data would have been ranked 2 and 3, then they will be both be ranked 2.5 if they are equal. (Note that the table does not correctly allocate ranks if three or more ranks are the same.) © MathsNet 2001