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 						  ![image.png](../assets/image_1686901196592_0.png)
 						- Property (iii) is called finite additivity.
 					- Axiomatic Definition of Probability ![section 1.4.pdf](../assets/section_1.4_1686901294123_0.pdf)
+						- A collection F of subsets of Ω is a σ-algebra if
+						  (i) Ω ∈ F ;
+						  (ii) F ∈ F =⇒ F ∈ F ;
+						  (iii) if Fn is a countable collection of sets, n = 1, 2, · · · such that
+						  Fn ∈ F for all n, then
+						- ![image.png](../assets/image_1686901503094_0.png)
 					- Properties of Probability
 			- LATER 学积分
 			  :LOGBOOK: