00:01
In this problem, it is said that you're trying to answer a multiple choice question.
00:04
There are five choices.
00:06
If you get the question right, you will gain one point.
00:09
If you get it wrong, you will lose one third of a point.
00:12
And you pick one of the choices at random, and we need to determine the expected value of the number of points you get.
00:18
Now, if x is the number of points you get, then we want to determine the expected value.
00:23
Now, this is equal to summation x times p of x, where x represents the values that x can take, and p of x represents the corresponding probability.
00:32
Now, first of all, consider the case in which you get the question right.
00:36
If you do that, you gain one point, so x will be one.
00:39
And what is the corresponding probability? that is the probability of getting it right.
00:43
Now there are five choices and there's only one correct choice out of them.
00:48
So 1 by 5 is the probability of getting it right...