00:01
For this exercise we have the probability mass function for the discrete random variable x, and for part a we are asked to calculate the expected value for x.
00:12
And for any discrete random variable, this is equal to the summation over all possible values of the random variable of x times the probability of x.
00:24
So for this variable, this is equal to 1 times .05 plus 2 times .15 plus 4.
00:36
Times .3 and so on.
00:48
And this comes out to 6 .75.
00:54
And then for b, we're asked to compute the variance of x.
01:00
For any discrete random variable, this is equal to the summation of x minus the mean squared times the probability of x.
01:16
So we have 1 minus the mean, that's 6 .75, squared times .05, plus 2 minus 0 .05, plus 2 minus 6 .75, squared times the probability of .15, and so on...