# Store

• December 25th 2008, 04:17 AM
magentarita
Store
A small grocery store realizes that they can model the number of people in the store using a Poisson distribution, with mean 6. What is the chance that 6 people will be in the store at any given time? (round, if necessary, to the nearest 10th of a percent)

1-50%

2-44.6%

3-16.1%

4-55.4%
• December 25th 2008, 04:37 AM
mr fantastic
Quote:

Originally Posted by magentarita
A small grocery store realizes that they can model the number of people in the store using a Poisson distribution, with mean 6. What is the chance that 6 people will be in the store at any given time? (round, if necessary, to the nearest 10th of a percent)

1-50%

2-44.6%

3-16.1%

4-55.4%

Substitute the information into the usual Poisson formula:

$\Pr(X = 6) = \frac{e^{-6} \, 6^6}{6!}$.

Multiply by 100 to convert into a percentage.
• December 25th 2008, 10:05 AM
magentarita
ok...
Quote:

Originally Posted by mr fantastic
Substitute the information into the usual Poisson formula:

$\Pr(X = 6) = \frac{e^{-6} \, 6^6}{6!}$.

Multiply by 100 to convert into a percentage.

I've never seen that formula before. This question was given on my final exam but the teacher did no cover the topic in class.
• December 25th 2008, 01:10 PM
mr fantastic
Quote:

Originally Posted by magentarita
I've never seen that formula before. This question was given on my final exam but the teacher did no cover the topic in class.

I wouldn't have thought you'd be given a specific question about the Poisson distribution on an exam unless you had studied that distribution in class.

Read (the first bit): 1.3.6.6.19. Poisson Distribution
• December 28th 2008, 08:06 AM
magentarita
ok...
Quote:

Originally Posted by mr fantastic
I wouldn't have thought you'd be given a specific question about the Poisson distribution on an exam unless you had studied that distribution in class.

Read (the first bit): 1.3.6.6.19. Poisson Distribution

I will visit the link suggested.
• December 30th 2008, 04:47 AM
HallsofIvy
Quote:

Originally Posted by magentarita
I've never seen that formula before. This question was given on my final exam but the teacher did no cover the topic in class.

Then go to your teacher and complain. But don't be surprized if he/she points out exactly when and where the topic was covered!
• January 1st 2009, 01:27 PM
magentarita
I would...
Quote:

Originally Posted by HallsofIvy
Then go to your teacher and complain. But don't be surprized if he/she points out exactly when and where the topic was covered!

I would complain but the fall 2008 semester ended.