00:01
We've been given some results here, grades by gender.
00:05
And we want the probability based on a randomly chosen student.
00:10
Okay, so i'll start by trying to draw up this graph.
00:14
So we have male, female, and grades.
00:20
A, b and c.
00:23
So males are 18, 17 and 14.
00:28
Females, 4, 16 and 15.
00:31
Okay.
00:39
Now, part a, the probability a randomly chosen student is male.
00:44
So for a lot of these, i'm going to be using a fraction.
00:47
On the denominator, i'm going to have all of the possibilities.
00:50
Every student i might choose.
00:53
Which for this first question is any of them.
00:56
On the numerator, i'm going to have all the ones that meet my criteria.
01:00
And this fraction works because each student has an equal probability of being chosen.
01:04
So if we have is 84 total students, then one in 84 chance of each one being chosen.
01:13
So for part a, i could pick any out of the 84, and how many of them are male? well, 49 are male.
01:23
So my answer is just going to be 49 divided by 84, which is 0 .583, the four decimal places.
01:41
Next, we want the probability that the randomly chosen student is male and got an a.
01:49
So we want both outcomes here.
01:53
One isn't enough.
01:54
So out of the 84 students we might choose, male and an a is only these.
02:00
18 of them.
02:01
Out of the 84 meet these criteria...