The relation between 2 series is called Correlation.

You will first learn about Covariance and how to calculate it. From there, you will learn about Karl Pearson's coefficient of Correlation, its notation and how to calculate it.

If X and Y are independent variables, COV(X,Y)=0 and coefficient of correlation is 0.

Sometimes, we may choose to grade the data in terms of numbers 1,2-----, from the highest or lowest value.

If 2 sets of data are ranked in this way, we get Spearman's coefficient of Correlation.

Learn how to calculate it in these videos. 

What happens if a rank is repeated?

We add a correction factor as illustrated in the lessons below.