# Norminv Function/Formula

• Hey, I need to do a series of calculations using the norminv function and some other things I'm unfamiliar with. Here is a description of what I need to do:

Quote

If you have Excel, you put in the daily odds, then get prob = 1/(1+odds), then zscore = norminv(p) and make the zscore negative if the odds were below chance. Then add up all the zscores and divide by sqrt(numdays), and convert back to probability with normdist(z).

Could I anyone give me step by step instructions on how to do this on Excel? I would be *deeply* appreciative. thanks a lot!

• Re: Norminv

Welcome to OzGrid Curtis!

Is this a homework assignment?

• Re: Norminv Function/Formula

Thanks for the welcome! Actually, I was tooling around with a statistics machine that measures psychic potential, and I need some way to figure out the outcomes, strange as it sounds. Its not a homework assignment - would that be bad if it was?

• Re: Norminv Function/Formula

Well, generally homework is to help someone learn by figuring it out themselves. The steps to do what you ask are actually spelled out pretty well by the instructions you quoted. Which step are you having trouble with?

• Re: Norminv Function/Formula

Accesing norminv...

• Re: Norminv Function/Formula

In Excel, it is a standard function that works just like any other function. If p is a probability, then
=NORMSINV(p)
will return the zscore associated with the value p. (I think from your description, you want NORMSINV rather than NORMINV.)

Incidentally, I don't see any reasonable interpretation for the calculation that results when you add up a number of zscores and then divide by the square root of the number. But then I don't know anything about "psychic potential."

• Re: Norminv Function/Formula

Okay, thanks. Its a random number generator.

One more questioN: I would just type '=norminv(p)' and that would give me the answer?

• Re: Norminv Function/Formula

The p, in all likelihood, is going to be a cell reference, so:

=NORMSINV(A1)

will give you the z score for the p value in cell A1.