00:01
A prof teaches a large class and schedules an examination for 7 p .m.
00:05
In different classrooms.
00:06
She estimated the probability in the table for the number of students who will call her at home in the hour before the examination in which classroom the exam will be held.
00:16
So we have a data set over here.
00:18
We have the number of calls at 0 to 5 and then we have the probability for each of this number of calls.
00:23
So the question says you should find the mean and standard deviation of the number of calls.
00:28
So we can see that distribution is actually a discrete probability distribution because the number of course is actually a discrete random variable.
00:37
For a discrete probability distribution, the formula for the expected value, which you also call the mean, it's actually close to summation x times p of x and the formula for the standard deviation is actually the square roots of variance.
00:57
And where the variance is across to summation x minus me where your mu is the expected value this is the e of x all squared times p of x so the first step is for us to create a new table for data set so we can we have x here we have a p of x we have zero we have one we have two we have three we have four and we have five so the p of x we have 0 .1 we have 0 .15 0 .1 0 .15 we also have 0 .19 and then we have a 0 .190 .111 so before we can be able to get the value of the variance we need to get the value of the expected value which is the mean so we need x times p of x so 0 .0 times 0 .0 .0.
01:59
1 times 0 .15.
02:02
2 times 0 .19.
02:07
So we have that to be 0 .38.
02:10
3 times 0 .26.
02:13
We have that to be 0 .7 8.
02:16
4 times 0 .19.
02:18
We have that to be 0 .76.
02:21
And 5 times 0 .11.
02:24
We have that to be 0 .55.
02:30
Hello, gamizam.
02:32
I'm going to say? no, my wife.
02:36
Okay...