Collect paired data values for two variables
Compute the mean of each variable
Subtract each mean from its corresponding values to get deviations
Multiply each pair of deviations
Sum all the products of deviations
Compute the sum of squared deviations for each variable
Divide the sum of products by the square root of the product of the two sums of squared deviations
Use the formula: r = Σ[(x – xÌ„)(y – ȳ)] / sqrt[Σ(x – xÌ„)² Σ(y – ȳ)²]
Verify the result is between -1 and 1