## Sample Size Calculation for discordance difference of zero

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# Sample Size Calculation for discordance difference of zero

Hello!

I am trying to calculate the sample size for a paired freq test using mcnemar.  I have estimated that my discordant proportions are p01=.0012 and p10=.0138.  My hypotheses are:

Ho: p01>=p10  OR p01-p10 >= 0

Ha: p01 < p10  OR p01-p10 < 0

Since I only care about the effect size if p01 > p10, I thought I should change the values of p01 and p10 to both = (0.0012+0.0138)/2 = 0.0075  Then, my proportion difference is 0; my reference proportion is 0.0075

However, when I try this in proc power, I end up not being able to test the effect size = 0 and receive the error message:

WARNING: The magnitude of the effect is zero in 4 scenarios in the output table.

My code is posted below.  Can someone help me to understand how to test this hypothesis?

Thanks!

proc power;

PAIREDFREQ

test=mcnemar

alpha=.05

power=.8 .85 .9 .95

npairs=.

discpropdiff = 0

refproportion = 0.0075

method=connor

dist=normal

sides=U

;

run;

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