00:01
When i test with 10 multiple choice and 10 multiple choice and 10 true false, then in the multiple choice have four choices.
00:13
Let's find the following probabilities.
00:16
So i'm going to start with the true false.
00:18
So we're only looking at the true false, and there's 10 of those.
00:21
We want to the probability of at least 7.
00:24
So that means we need to know the probability of 7, probability of 8, probability of 9, and the probability of 10.
00:33
And then we're going to add all those together.
00:36
So we're only looking at these 10.
00:38
So the probability of 7.
00:40
We don't know which group of 7.
00:41
So we're going to say a combination of 10 picking 7 at a time.
00:46
And then we get 7 correct.
00:48
So our correct answers is a 50 % chance.
00:51
And then our incorrect is also 50 % chance.
00:54
So that's going to be timed to the third power.
00:57
When we look at the 8, we're going to do the same thing.
01:00
So we're going to have eight questions.
01:03
Correct the probability and then we're going to have two questions incorrect.
01:09
For nine we're going to take a combination of ten picking nine at a time so the correct is going to be 0 .5, 9 of those and then 0 .5 for 1 and then for the probability then we're going to do the 10 we don't need to do a combination because there's only one group of 10 we can just say 0 .5 to the 10th power.
01:29
We can go to our calculator get each one of those and add them together.
01:34
Let's go to the next one and get it set up.
01:36
We're looking at multiple choice now.
01:38
So we need the probability of 6, 7, 8, 9, and the probability of 10.
01:49
So we're going to come over here, multiple choice.
01:52
There's 10, 4 choices...