The POWER Procedure
PAIREDFREQ Statement
PAIREDFREQ <options>;
The PAIREDFREQ statement performs power and sample size analyses for McNemar’s test for paired proportions.
Summary of Options
Table 91.19 summarizes the options available in the PAIREDFREQ statement.
Table 91.19: PAIREDFREQ Statement Options
Table 91.20 summarizes the valid result parameters in the PAIREDFREQ statement.
Table 91.20: Summary of Result Parameters in the PAIREDFREQ Statement
Dictionary of Options
Restrictions on Option Combinations
To specify the proportions, choose one of the following parameterizations:
discordant proportions (using the DISCPROPORTIONS= option)
difference and sum of discordant proportions (using the DISCPROPDIFF= and TOTALPROPDISC=options)
difference of discordant proportions and reference discordant proportion (using the DISCPROPDIFF= and REFPROPORTION= options)
ratio of discordant proportions and reference discordant proportion (using the DISCPROPRATIO= and REFPROPORTION= options)
ratio and sum of discordant proportions (using the DISCPROPRATIO= and TOTALPROPDISC=options)
paired proportions and correlation (using the PAIREDPROPORTIONS= and CORR= options)
proportion difference, reference proportion, and correlation (using the PROPORTIONDIFF=, REFPROPORTION=, and CORR= options)
odds ratio, reference proportion, and correlation (using the ODDSRATIO=, REFPROPORTION=, and CORR= options)
relative risk, reference proportion, and correlation (using the RELATIVERISK=, REFPROPORTION=, and CORR= options)
Option Groups for Common Analyses
This section summarizes the syntax for the common analyses that are supported in the PAIREDFREQ statement.
McNemar Exact Conditional Test
You can express effects in terms of the individual discordant proportions, as in the following statements. Default values for the TEST=, SIDES=, ALPHA=, and NULLDISCPROPRATIO= options specify a two-sided McNemar test for no effect with a significance level of 0.05.
proc power;
pairedfreq dist=exact_cond
discproportions = 0.15 | 0.45
npairs = 80
power = .;
run;
You can also express effects in terms of the difference and sum of discordant proportions:
proc power;
pairedfreq dist=exact_cond
discpropdiff = 0.3
totalpropdisc = 0.6
npairs = 80
power = .;
run;
You can also express effects in terms of the difference of discordant proportions and the reference discordant proportion:
proc power;
pairedfreq dist=exact_cond
discpropdiff = 0.3
refproportion = 0.15
npairs = 80
power = .;
run;
You can also express effects in terms of the ratio of discordant proportions and the denominator of the ratio:
proc power;
pairedfreq dist=exact_cond
discpropratio = 3
refproportion = 0.15
npairs = 80
power = .;
run;
You can also express effects in terms of the ratio and sum of discordant proportions:
proc power;
pairedfreq dist=exact_cond
discpropratio = 3
totalpropdisc = 0.6
npairs = 80
power = .;
run;
You can also express effects in terms of the paired proportions and correlation:
proc power;
pairedfreq dist=exact_cond
pairedproportions = 0.6 | 0.8
corr = 0.4
npairs = 45
power = .;
run;
You can also express effects in terms of the proportion difference, reference proportion, and correlation:
proc power;
pairedfreq dist=exact_cond
proportiondiff = 0.2
refproportion = 0.6
corr = 0.4
npairs = 45
power = .;
run;
You can also express effects in terms of the odds ratio, reference proportion, and correlation:
proc power;
pairedfreq dist=exact_cond
oddsratio = 2.66667
refproportion = 0.6
corr = 0.4
npairs = 45
power = .;
run;
You can also express effects in terms of the relative risk, reference proportion, and correlation:
proc power;
pairedfreq dist=exact_cond
relativerisk = 1.33333
refproportion = 0.6
corr = 0.4
npairs = 45
power = .;
run;
McNemar Normal Approximation Test
The following statements demonstrate a sample size computation for the normal-approximate McNemar test. The default value for the METHOD= option specifies an exact sample size computation. Default values for the TEST=, SIDES=, ALPHA=, and NULLDISCPROPRATIO= options specify a two-sided McNemar test for no effect with a significance level of 0.05.
proc power;
pairedfreq dist=normal method=connor
discproportions = 0.15 | 0.45
npairs = .
power = .9;
run;