00:01
Ok, part a, i want to prove that this is actually a distribution for probability.
00:12
What we do for that is add up all the numbers on the bottom here and see what we get.
00:19
And in fact, if i do that, the sum is 1, which implies it is a correct distribution.
00:28
That's part a.
00:31
Now part b, i want to work out the mean, or the mean mu is e of x, the expected value of the variable.
00:50
And that is sigma x times p of x.
00:56
So here then, what we have, 0 times 0 .2401, 1 times 0 .4116.
01:08
In other words, i'm doing this times this, plus this times this, plus this times this, and so on all the way along.
01:19
So 2 times 0 .2646, 3 times 0 .0756, and 4 times the last one, 0 .0081.
01:39
So that i work out on a calculator, and that is 1 .2.
01:46
Now part c, i want to work out the value v of x equals exactly 1 degree, and that is this one here, 0 .4116.
02:06
Now, to find that on the ti -84 plus, what you do is as follows.
02:13
Press 2nd, followed by vars, v -a -r -s, on the right, just below the arrow keys.
02:20
That gives the menu for distributions.
02:22
You can't see binomial yet, but what you do is you go down, that's number 9 at the bottom, until you reach binompdf, item a on the list.
02:36
So binompdf, press enter.
02:41
It will say trials, that's number of people here, adults, so it's 4.
02:45
P -value is going to be 0 .3 from 30 % of a degree, so i put it in decimal form, and the x -value is 1, which you see here...