00:01
Okay, we are told 11 % of the population are smokers, which means i can write down p of being a smoker is a 0 .11 chance, which implies p of a non -smoker is 1 minus that, so 0 .89.
00:29
Now, in part a, what we have is p of all 25 not smokers.
00:41
So 25 non -smokers will be .89 power of 25.
00:51
And that i work out on a calculator.
00:58
0 .05429.
01:05
29, so if we want here is in fact four places.
01:12
So 0543 is the answer to four decimal places.
01:23
Now in part b what we have is the chance exactly five smoke.
01:34
So p of five smoke.
01:39
So that's 0 .11 power 5.
01:47
0 .11 power 5 .89.
01:53
Now there are 25 adults 5 are smoking so 20 not smoking and this is a binomial type problem so here a number of ways will be 25 5 and this i can work out on the back litter is 25 c5 and other the ti 84 plus press the math button on the left go across to pr ob with the arrow keys down to ncr just type in 25c5 and we get 53 ,130 and this i can now work out so i times 531310 by point 1 1 1 power of 5 and times that 5 .89 power of 20.
02:54
So here i get 0 .0 .8319, so 832 to 4 places.
03:07
Now that i can do a bit faster on the ti -84 plus get the function called binom pdf.
03:18
And to get that, press second, the blue button, followed by vars, v -a -r -s, on the right, just below the arrow keys.
03:29
Then that brings up the menu for distributions.
03:31
You can't see it yet.
03:33
Over the arrow key, go down past number 9 at the bottom.
03:37
Keep going into your reach item a, which is binom pdf.
03:42
Press enter.
03:44
It will say trials.
03:45
Or trials are a number of adults here, 25.
03:50
The p value is number of smokers, sorry, is a chance of smokers.
03:53
So 0 .11 is the v value.
03:57
And the x value is there are five smokers.
04:00
So 5.
04:02
That's the input.
04:03
25 .115.
04:06
Choose paste.
04:08
Press enter.
04:09
And, of course, get the same result.
04:11
0 .0832.
04:14
Either way is correct.
04:16
And in fact, both ways, should be known.
04:20
Now, part c, the of exactly 7 smoke.
04:27
Again, either way.
04:31
Is good...