diff --git a/education/statistics/Correlation and Regression.md b/education/statistics/Correlation and Regression.md
index 462b59d..79aea81 100644
--- a/education/statistics/Correlation and Regression.md	
+++ b/education/statistics/Correlation and Regression.md	
@@ -29,7 +29,9 @@ Correlation is between `-1` and `1`. Correlation near 1 means tight clustering,
 Put the $x$ values into $L1$, put the $y$ values into $L2$. 
 
 1. Convert the $x$ values to standard units ($z$). Convert the $y$ values to standard units.
-2. Multiply the standard units for each ($x$, $y$) pair. 
+$$ z = \frac{x-\bar{x}}{\sigma_x} $$
+2. Multiply the standard units for each ($x$, $y$) pair in the sets
+$$ x * y = $$
 3. Find the average of the values from step 3, this is $r$.
 $$ z_x = \frac{L_1-\bar{x}}{\sigma_x} $$
 https://www.thoughtco.com/how-to-calculate-the-correlation-coefficient-3126228