Question: how to find the correlation coefficient from a set of data?
Answer: Find the mean of all the x-values. Find the standard deviation of all the x-values (call it sx) and the standard deviation of all the y-values (call it sy). ...  For each of the n pairs (x, y) in the data set, take. Add up the n results from Step 3. Divide the sum by sx ∗ sy.