00:01
From the textbook, we are given the formula for the mean of a wibo distribution.
00:07
In this exercise, we show that this is true by using the definition for the expected value of x.
00:22
Now, by definition, the expected value is the integral over all values of x times the density function.
00:37
And the density function for a wibol is given as follows.
01:01
Now the hint given in the question is to substitute y for x over beta to the exponent alpha.
01:25
This substitution means that x is equal to beta times y to the exponent 1 over alpha.
01:36
Also we have dy is equal to alpha times x to the alpha minus 1 over beta to the exponent alpha dx.
02:14
Now carrying out the substitution, we only have to integrate above zero, since the ybel is only greater than zero for x is greater than zero.
02:29
So instead of x we are going to put in the substitute...