00:01
In this one, we really have a weighted mean in part a because we have the number of classes and the size, in this case, 1, 8, 1, 4, size being 20, 60, 80, 100.
00:27
Our weighted mean would be the product of those numbers, and add them up, divide by 14.
00:36
So 1 times 20 is 20, 60 times 80 is 480, 80 times 1 is 80, 100 times 4 is 400, and that adds up to 980.
00:53
So x bar is 980 divided by 14 or 70.
01:19
So b, you want the probability distribution, which is very similar.
01:30
We have the size of the class.
01:34
20, 60, 80, 100.
01:41
Probability.
01:43
Well, there was 21 class with 20, so 1 times 20 is 20 out of 980, which is 149th.
01:59
60 times 8 is 480, 980, which is 2449th.
02:05
80 times 1 is 80 out of 980.
02:13
180, which is 449th.
02:32
And 100 with four of those, that's 400 out of 980, 20 out of 5.
02:40
Well, if we want the mean of that, we take size times the probability.
02:57
So 20 times 149th is 20409ths.
03:01
24 times 60.
03:32
60 times 24 is 1440 out of 49.
03:40
I'm just leaving my stuff in fractions.
03:45
320 out of 49.
03:49
2 ,000 out of 49.
03:52
And if we add those up, we can get the mean...