diff --git a/transform.Rmd b/transform.Rmd
index 7adcb3e..676de52 100644
--- a/transform.Rmd
+++ b/transform.Rmd
@@ -676,7 +676,7 @@ Just using means, counts, and sum can get you a long way, but R provides many ot
       )
     ```
 
-*   Measures of spread: `sd(x)`, `IQR(x)`, `mad(x)`. The mean squared deviation,
+*   Measures of spread: `sd(x)`, `IQR(x)`, `mad(x)`. The root mean squared deviation,
     or standard deviation or sd for short, is the standard measure of spread.
     The interquartile range `IQR()` and median absolute deviation `mad(x)`
     are robust equivalents that may be more useful if you have outliers.