Well, my question now is, where is the discussion that tells exactly what
Smith's workbook consists of and how to use it? It's pretty useless if you
just get confronted with this sheet full of God knows what! Y'all have
sent me to this page, but no clue what they do!

--
Yours,
Dora Smith
Austin, TX

"Mike Middleton" wrote in message
...
Dora -

The functions are available when the examples.xls worksheet is open.

You enter the function in a worksheet cell.

I think you may want to use Smith's critpoiss function. For example, if
you enter =critpoiss(7,0.99) into a worksheet cell, where 7 is the mean of
the Poisson distribution and 0.99 is the cumulative probability, the
function returns the value 14.

As I wrote earlier, I have lost track of your original thread, so I don't
know the relevant values for your situation.

To view the VBA code for the functions, press Alt-F11 and open Module1.

Also, the terminology "confidence interval" usually refers to a range
based on analyzing a random sample. I think what you desire is usually
called a critical value, e.g., a value such that the cumulative
probability is less than a specified probability.

- Mike
http://www.mikemiddleton.com

"Dora Smith" wrote in message
...
I can't find in the Smith site anywhere instructions on how to use them.
Do I copy and paste something? Insert values into the worksheet?

--
Yours,
Dora Smith
Austin, TX

"Jerry W. Lewis" wrote in message
...
Ian Smith's library of probability functions includes functions for
Poisson
confidence intervals. You do not have to know VBA to use them, you just
have
to be willing to use a workbook that has VBA code in it. You use them
in
cell formulas, just like native Excel worksheet functions. The
worksheet in
http://members.aol.com/iandjmsmith/Examples.xls
gives example of the use of each function.

If you do not want to use the normal approximation with your large
numbers,
then there is no alternative in Excel to using the Smith library. Prior
Excel 2003, POISSON(,,TRUE) fails to return values well below a mean of
1000.
In Excel 2003 and Excel 2007, POISSON(,,TRUE) does return values for
large
means, but they are not to be trusted! For instance POISSON(x,x,TRUE)
should
converge toward 0.5 for large x, but instead it converges toward 1. The
Smith functions handle these calculations correctly, and AFAIK are the
best
double precision implementation available anywhere.

If the presence of VBA under the hood is a show stopper, then consider
downloading an using Stephen Bye's Excel compatible spreadsheet Spread32
http://www.byedesign.freeserve.co.uk/
which has a far more accurate POISSON function (with a larger working
range)
than either Excel 2003 or 2007.

Jerry

"Dora Smith" wrote:

OK, I understand why it makes more sense to use the normal
distribution, on
our hundreds of thousands of records, but my boss is not convinced -
mabye
because he knows the Poisson distribution is skewed to the left, and he
said
something about getting higher probabilities than 97%. I dunno. Maybe
the purpose has to do with improving performance.

My question now is, can Excel generate one-tailed confidence intervals
for
the Poisson distribution? In other words, is there a way to plug a
level of probability you want to achieve in and have it give you the
number
of records one has a 99% probability of achieving?

If not, what plugins for Excel are available to accomplish that -
without
needing to know visual basic or something to use them?

I have an idea not, but I'm double checking.

--
Yours,
Dora Smith
Austin, TX