问一道题：NO.PZ2016062402000006 [ FRM I ]

NO.PZ2016062402000006问题如下The ranm variable X with nsity function f(x)=1b−af(x)=\frac1{b-a}f(x)=b−a1​ for a x an0 otherwise, is saito have a uniform stuibution over (a,b).Caculate its mean. A.a+b2\frac{a+b}22a+b​B.a−b2\frac{a-b}22a−b​C.a+b4\frac{a+b}44a+b​a−b4\frac{a-b}44a−b​The meis the center of the stribution, whiis the average of a anb.该知识点在讲义哪里，麻烦注明

老师，这在视频里有哪块讲解的呢

     老师，想请问一下，这里的均值是指X取值的均值吗

这道题怎么理解。