<p>设随机变量<img max-width="300" src="https://file.gaojiufeng.cn/learnAppQuestion/c6/58/c658d989d92c12a3070cfb96b0ec14bb.jpg" style="width: 100%;height: auto;">独立同分布，且<img max-width="300" src="https://file.gaojiufeng.cn/learnAppQuestion/20/ea/20eafce2308cc4c133ad139aa1917886.jpg" style="width: 100%;height: auto;"><img max-width="300" src="https://file.gaojiufeng.cn/learnAppQuestion/b2/7f/b27f6169788cfcf09704e36a7f9c62e9.jpg" style="width: 100%;height: auto;"></p>