diff --git a/education/statistics/Correlation and Regression.md b/education/statistics/Correlation and Regression.md
index 7dd9c34..08fef55 100644
--- a/education/statistics/Correlation and Regression.md	
+++ b/education/statistics/Correlation and Regression.md	
@@ -112,6 +112,7 @@ The distance of an individual point from the regression line. This only applies
 $$ \sqrt{1-r^2}(\sigma_y) $$
 - On a least squared regression line, the 1 r.m.s error away will contain $2\sigma$ of the data, and it should loosely mirror a normal curve. 
 - To approximate the R.M.S error for a scatter diagram, take a high value and a low value for a given $x$ coordinate, and divide by 4, because r.m.s error is within $2\sigma$ of either side of the line. 
+- 68% = $2\sigma$, 95% = $4\sigma$
 
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 # Terminology