burt wrote:
>
> It seems that someplace in my statistical education I read or heard one
> of my teachers make the following statement: When the occurrence of rare
> events follows a Poisson process, then a characteristic of this process
> is as follows: Usually there are long periods of time between the
> events occurring, but occasionally the event may happen several times in
> a relatively short period of time.
> Can anyone provide a reference to this???
>
The Poisson distribution describes the rate of occurrence of rare
"objects" (events in the time period, things in some defined area or
volume, etc.) which are independent of each other. You need to find an
average to estimate the Poisson distribution; in your example it will be
the mean number of events in the defined time period.
Of course, PD will have the highest density around the average. Surely
you can have quite large values in the right tail of the distribution.
However it is quite difficult to address the scenario you proposed
without concrete data.
I would suggest to download some statistic tables calculating PD and
play with it.
A freeware can be downloaded from the Cytel Software.
I liked the free program which was advertised a couple of weeks ago on
this list
http://www.ucs.louisiana.edu/~kxk4695/StatCalc.htm/
You can also experiment on-line - some www pages have java applets. Try
to Google "Poisson distribution" to find learn more.
Regards,
k
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