00:01
Okay, we are told a store gets on average 12 customers per hour, so that we'll call mu the average.
00:10
And this is a quasson and i want to work out in part a, the chance of getting 15 customers in the one hour period.
00:23
And for this, use the function called quason pdf on the ti 84 plus calculator.
00:34
And you'll find that function by pressing second followed by vars on the right just below the arrow keys.
00:46
That brings up the menu for distributions.
00:49
You can't see it yet but press the arrow key and go down past number nine.
00:55
Keep going until you reach item d.
00:59
Press on pdf, press enter and the input is the mean number per hour.
01:06
Which is mu, that will be 12, and the x value is the 15.
01:14
So we have plus on pdf 1215 and that paste that and the answer is 0 .07239.
01:31
And what they want here is okay no mention of accuracy so we'll say 0 .0724 to 4.
01:41
Decimal places.
01:47
Now in part b what i want is more than a five so p of x for customers bigger than five which means p of six seven eight nine and so on customers per hour.
02:10
Now that you work out by going backwards from one.
02:14
It's a certain event one minus p of zero one, two, three, four, five.
02:23
Why do that? well, this item here, i can work out on a calculator.
02:30
And that will be queson, c, df, c for cumulative, we'll add up 0, 1, 2, 3, 4, 5.
02:41
And again, the same input, two numbers, 12 for the mean, and 5 is the value number you see here...