00:01
Okay, we are told that the number of emails received per hour follows a poisson distribution.
00:06
So you can say then x corresponds to a poisson distribution where the parameter is 5.
00:13
The mean value is 5 per hour.
00:16
I want to work out in one hour the chance that there are zero emails and for that use a ti -84 plus calculator for one similar and what you want is the function poisson pdf, poisson pdf, which you will find by pressing 2nd followed by vars v -a -r -s on the right by the arrow keys.
00:43
That gives the menu for distributions.
00:46
You can't see it yet, but go down with the arrow key past number 9 at the bottom.
00:51
Keep going down till you reach item d, poisson pdf.
00:55
Press enter.
00:56
The input is the mean which is 5 per hour and the x value is 0.
01:05
So just type in poisson pdf 5 0 paste enter and we get 0 .006737 and so on.
01:21
What they want here is no mention of accuracy.
01:27
So we'll say then 0 .00674 correct to 3sf.
01:35
That's the first one.
01:36
Okay, next we have the chance of getting 3 or more.
01:42
So at least 3, which means of course 3, 4, 5, 6, 7, 8, 9 and so on.
01:48
And for this you have to work backwards and do 1 minus what you don't want to occur which is x to be 2 or less.
01:57
Now that i work out again with the ti -84 plus.
02:02
This time the function is poisson cdf.
02:06
Cdf, c stands here for cumulative.
02:09
That will work out for you...