Revision:Correlation

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Product Moment Correlation

The product moment correlation is a process which indicates the linear strength between the actual values of two sets of data.

It's formula is given by:

Where:

Example

Find the product moment correlation of the following set of data:

First we must calculate the values of x², y² and xy.

Doing that gives:

We then total up each giving, giving
We then put these into our formula, giving:

0.954 is therefore our coefficient of x. It is worth that: A coefficient close to 1 indicates strong positive correlation whilst a coefficient close to -1 indicates strong negative correlation. A coefficient close to 0 indicates little correlation.

Spearman's Rank