Conditional Expectation

如果我想用simulation揾E[X|t<10]
我篩咗符合t<10嘅X_i出黎
以上嘅expectation係咪mean(X_i) / P(t<10)?
定淨係mean(X_i)?

P(H | A) P(A) = P(A | H) P(H)

有冇stat師兄入黎講解下