00:01
Okay, we are told that 55 % of the students are male, which means a random choice.
00:08
P of male is going to be 0 .55, which implies p of female is 1 minus that, 0 .45.
00:20
So binomial type distribution, success and failure.
00:26
Here success, the p value is going to be 0 .55.
00:32
Now the first question says in part a, p of exactly four male students from 20.
00:44
So we'll say x then is number of male students.
00:49
So i want to work out p of x equals four.
00:53
Now, one way is doing this.
00:57
0 .55 has to occur four times, which implies female 0 .45 must occur 16 times.
01:06
For 20 students and this can be done different ways number of ways 24 and 24 you can work out it's 20 factorial 16 factorial 4 factorial that's from first principles basically the faster is with the t i 84 plus calculator the function called binom or binomial pdf and that will be well, you'll find it first of all by pressing second on the ti -84 plus, the blue button, followed by vars, v -a -r -s, on the right, just below the arrow keys.
01:52
That brings up the menu for distributions.
01:55
What you want is off the screen at the moment.
01:58
Go down past number 9, here the bottom, use the arrow keys until you reach item a, bin -on pdf.
02:05
Press enter.
02:07
The input is trials, here that number of students.
02:10
So is 20.
02:11
The p value is chance of the male 0 .55 and the x value here is the 4.
02:19
I want 4 males.
02:21
So type it in 20 .554 and get the answer which is 0 .001 -2535.
02:37
And what they want here, okay, no mention of accuracy.
02:41
So we'll just do 3sf.
02:44
So 0 .00125 is the first one.
02:53
Okay, part b is p of male students more than 9...
