Christopher -

=STANDARDIZE(0.31,0.49,SQRT(0.5*0.5/998))

returns -11.37280968

Your parentheses are misplaced in
z = (p-Po)/square root((Po(1-Po))/N)
The expression should be
z = (p-Po)/square root(Po(1-Po)/N)

- Mike Middleton
http://www.DecisionToolworks.com
Decision Analysis Add-ins for Excel



"Christopher" wrote in message
...
To all,

Needed some help on finding a formula to use in excel to calculate a z-
score that is comparing a sample proportion to a population
proportion. Here's the data:

Sample proportion = 0.31
N = 998
Population proportion = 0.49

I can find a z-score using a formula by hand: (z-score = -11.39), but
wanted to calculate in excel for many other variables. This is the
formula I used by hand:

p = sample proportion
Po = population proportion
alpha = 0.05 (z-critical = plus/minus 1.96)
non-directional test

z = (p-Po)/square root((Po(1-Po))/N)

When I use the standardize function in excel it gives me = -0.1153.

Any suggestions?
Thanks!