I've tested binomial and chi-squared approximation (or z) and I found that even with very large samples, the probability obtained are different. The difference is often small (especially when N is large and when P is close to .5), but knowing that many people will consider probabilities of .051 and .049 as quantitatively close but qualitatively different (significant vs non significant), I am reluctant to use any normal approximation when the binomial probability can be computed.
"Rich Ulrich" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > State the actual proportions. > And state where the power estimate comes from. > > Use the 2x2 table and chi squared, when the Ns are big > enough to justify approximations. . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
