diff --git a/Running Start/CSB320 - Machine Learning Concepts/Class 4-23 (Model Validation & Evaluation).md b/Running Start/CSB320 - Machine Learning Concepts/Class 4-23 (Model Validation & Evaluation).md
index 912df09..38fc0fa 100644
--- a/Running Start/CSB320 - Machine Learning Concepts/Class 4-23 (Model Validation & Evaluation).md	
+++ b/Running Start/CSB320 - Machine Learning Concepts/Class 4-23 (Model Validation & Evaluation).md	
@@ -66,3 +66,4 @@ There are many ways to evaluate the performance of models. This is necessary to
 ## Loss Functions
 Loss functions are meant to quantify the difference between observed values and the predictions of a model. They can be used to minimize loss and improve model performance.
 ### Absolute Loss
+$$Y_{i} - \hat{Y}_{i}$$