diff --git a/slides/sections/4.md b/slides/sections/4.md
index a07164d..119e714 100644
--- a/slides/sections/4.md
+++ b/slides/sections/4.md
@@ -73,9 +73,9 @@ How to estimate sample median, mode and FWHM?
 
 \Begin{block}{Algorithm}
 ::: incremental
-1. Find the smallest interval containing half points
-2. Repeat on the new interval (called modal)
-3. If the interval has less than two points, take average
+  1. Find the smallest interval containing half points
+  2. Repeat on the new interval (called modal)
+  3. If the interval has less than two points, take average
 :::
 \End{block}
 
@@ -222,3 +222,19 @@ Root finding (Brent-Dekker) for $\quad f_{\varepsilon}(x_{\pm}) =
 ## Sample FWHM
 
 ![](images/kde.pdf)
+
+
+## Bootstrap
+
+Estimating confidence interval:
+
+. . .
+
+\Begin{block}{Algorithm}
+::: incremental
+  1. Sample $N$ points from PDF
+  2. Sample with replacement $M$ times
+  3. Apply the test to each new sample
+  4. Compute mean and standard deviation
+:::
+\End{block}