diff --git a/education/statistics/random-variable.md b/education/statistics/random-variable.md
index 0689a22..7257eb3 100644
--- a/education/statistics/random-variable.md
+++ b/education/statistics/random-variable.md
@@ -2,7 +2,7 @@
 title: 隨機變數 (Random Variable)
 description: 
 published: true
-date: 2025-12-28T16:54:25.985Z
+date: 2025-12-28T16:58:42.847Z
 tags: 
 editor: markdown
 dateCreated: 2025-12-28T16:41:51.938Z
@@ -14,6 +14,11 @@ dateCreated: 2025-12-28T16:41:51.938Z
 
 A set of probability value **p~i~** assigned to each of the values taken by the discrete random variables **x~i~**.
 
+$0 \leq p_i \leq 1$ and $\sum_{p_i} = 1$
+
+Probability
+$P(X=x)=p_i$
+
 ### Cumulative Distribution Function (CDF)
 
 ## Continuous