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From: Robert Feyerharm on 18 Dec 2009 16:56
I have a question regarding the power procedure for a paired case-control
design using the McNemar test.

I'm using proc power to estimate the necessary sample size for a proposed
public health study that will compare infant mortality rates between two
groups, a control group of mothers who received no public health
intervention & a treatment group who participated in the Children First or
Healthy Start programs. Mothers will be matched based on similar
demographic variables (race, age, education, etc.). We want to detect a
reduction in infant mortality from say 15 deaths per 1,000 live births
(p0=.015) to 10 deaths per 1,000 live births (p1=.010), with power=.80 and
alpha=.05.

Here's my code:

proc power;
pairedfreq dist=normal method=connor
test=mcnemar
corr=???
alpha=.05
relativerisk = .67
refproportion = 0.015
npairs = .
power = .8;
run;

My question: What is the correct value to use for the correlation
coefficient for exposure between cases and their matched controls? Since
every matched pair will be discordant (the case mother participates in the
health program & her control doesn't), is corr=0 appropriate?

Thanks in advance!

Robert Feyerharm
Oklahoma State Department of Health
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