You can calculate the correlation between two variables by a measurement known as the Pearson Product Moment Correlation (also called Pearson's correlation or Spearman rank correlation). You may know that you can make this calculation, often designated by the letter "r," using statistical software, such as SPSS or R. But did you know that you can even do it with good-old Microsoft Excel?

Put the values of the two variables you wish to correlate into two columns of the same length. For example, say you have data about the heights and weights of 50 people, and want to calculate the Pearson correlation between the two. Put the data into two columns: the heights in cells 1 to 50 of column A, and the widths in cells 1 to 50 of column B.

Select an unused cell and type "=CORREL(" (without the quotes). After typing the first open parentheses, select all of the cells in your first column, type a comma, select all of the cells in your second column, and type the closing parentheses ")". In this example, since the data was in cells 1 to 50 of column A and cells 1 to 50 of column B, you could also simply type:

\=CORREL(A1:A50,B1:B50)

Either method should yield the same result.

Press "Enter." The cell now contains the value of the correlation between the two columns.