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# Reading Poisson distribution tables help! S1

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1. Reading Poisson distribution tables help! S1
I understand how to read a poisson distribution table with lambda being 0.5,1,1.5,2,2.5 etc.. but what must I do when lambda is 2.4?

X ~ Po(2.4)

And trying to find P(3<X<6) [Both inclusive]

So: P(X<6) [Inclusive] - P(X<2) [Inclusive]

Any help?
2. Re: Reading Poisson distribution tables help! S1
If your tables don't list the value, resort to a calculator which isn't too much work for a handful of cases.
3. Re: Reading Poisson distribution tables help! S1
(Original post by ian.slater)
If your tables don't list the value, resort to a calculator which isn't too much work for a handful of cases.
This question says in bold With the use of tables, so there must be a way of finding the values with the 2.4

I was thinking along the lines of finding 2.5 on the tables and minus 0.1 on the tables if that's even possible?
Last edited by Ryan44; 27-05-2012 at 23:46.
4. Re: Reading Poisson distribution tables help! S1
(Original post by Ryan44)
This question says in bold With the use of calculators, so there must be a way of finding the values with the 2.4

I was thinking along the lines of finding 2.5 on the tables and minus 0.1 on the tables if that's even possible?
The Poisson distribution with parameter lambda is defined by:

P(X = n) = (e^-lambda) (lambda^n)/n!

So by putting n=3 say in this you can work out P(X=3). Add a few of those up and you have your answer.
5. Re: Reading Poisson distribution tables help! S1
(Original post by ian.slater)
The Poisson distribution with parameter lambda is defined by:

P(X = n) = (e^-lambda) (lambda^n)/n!

So by putting n=3 say in this you can work out P(X=3). Add a few of those up and you have your answer.
Sorry man I meant With the use of tables
6. Re: Reading Poisson distribution tables help! S1
(Original post by Ryan44)
Sorry man I meant With the use of tables
I'm surprised then that the board you use doesn't supply tables with a parameter of 2.4. For example the MEI tables http://www.mei.org.uk/files/pdf/formula_book_mf2.pdf do.
7. Re: Reading Poisson distribution tables help! S1
(Original post by ian.slater)
I'm surprised then that the board you use doesn't supply tables with a parameter of 2.4. For example the MEI tables http://www.mei.org.uk/files/pdf/formula_book_mf2.pdf do.
The board I'm with is the WJEC, I'm expecting the tables given in the exam to work with what's needed in one of the questions, although at the moment I'm just using the top 2 results after searching 'Poisson distribution table' into Google.

I was just wondering whether there is some sort of simple calculation needed using the tables to make Lambda 2.4. I'm confident with working it out without the use of tables btw
8. Re: Reading Poisson distribution tables help! S1
(Original post by Ryan44)
The board I'm with is the WJEC, I'm expecting the tables given in the exam to work with what's needed in one of the questions, although at the moment I'm just using the top 2 results after searching 'Poisson distribution table' into Google.

I was just wondering whether there is some sort of simple calculation needed using the tables to make Lambda 2.4. I'm confident with working it out without the use of tables btw
Maybe you are meant to use:

X~Poisson(lambda) and Y~Poisson(mu) => X+Y ~ Poisson(lambda + mu)

creatively. If you could find two values in your tables that add/subtract to 2.4 and then worked out loads of cases you could get there ...

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Last updated: May 28, 2012
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