设X服从指数分布，则 Xgt 4|Xgt 2 =P Xgt 4 4mid X>2}=PX>4" data-width="294" data-height="26" data-size="3710" data-format="png" style="max-width:100%">（）。A.对B.错
设X服从指数分布，则
4\mid X>2\right\}=P\left\{X>4\right\}" data-width="294" data-height="26" data-size="3710" data-format="png" style="max-width:100%">（）。
A.对
B.错
题目解答
答案
∵X服从指数分布
∴
0}_{0,其他} \right." data-width="159" data-height="45" data-size="2860" data-format="png" style="max-width:100%">
∴
2\right\}=\int_2^{+\infty}\lambda e^{-\lambda x}dx" data-width="254" data-height="54" data-size="4250" data-format="png" style="max-width:100%">
4\right\}=\int_4^{+\infty}\lambda e^{-\lambda x}dx" data-width="254" data-height="54" data-size="4213" data-format="png" style="max-width:100%">
∴
4\mid X>2\right\}=\frac{P\left\{X>4,X>2\right\}}{P\left\{X>2\right\}}" data-width="367" data-height="59" data-size="6537" data-format="png" style="max-width:100%">
4\right\}}{P\left\{X>2\right\}}" data-width="126" data-height="59" data-size="3190" data-format="png" style="max-width:100%">
4\right\}" data-width="118" data-height="26" data-size="1755" data-format="png" style="max-width:100%">
故此题选B