The POWER Procedure 
ONECORR Statement 
The ONECORR statement performs power and sample size analyses for tests of simple and partial Pearson correlation between two variables. Both Fisher’s z test and the test are supported.
Table 68.6 summarizes categories of options available in the ONECORR statement.
Task 
Options 

Define analysis 

Specify analysis information 

Specify effects 

Specify sample size 

Specify power 

Control sample size rounding 

Control ordering in output 
Table 68.7 summarizes the valid result parameters in the ONECORR statement.
Analyses 
Solve For 
Syntax 

TEST=PEARSON 
Power 

Sample size 
specifies the level of significance of the statistical test. The default is 0.05, corresponding to the usual 0.05 100% = 5% level of significance. See the section Specifying Value Lists in Analysis Statements for information about specifying the numberlist.
specifies the correlation between two variables, possibly adjusting for other variables as determined by the NPARTIALVARS= option. See the section Specifying Value Lists in Analysis Statements for information about specifying the numberlist.
specifies the underlying distribution assumed for the test statistic. FISHERZ corresponds to Fisher’s normalizing transformation of the correlation coefficient. T corresponds to the transformation of the correlation coefficient. Note that DIST=T is equivalent to analyses in the MULTREG statement with NTESTPREDICTORS=1. The default value is FISHERZ.
specifies the assumed distribution of the first variable when DIST=T. The second variable is assumed to have a normal distribution. MODEL=FIXED indicates a fixed distribution. MODEL=RANDOM (the default) indicates a joint bivariate normal distribution with the second variable. You can use the aliases CONDITIONAL for FIXED and UNCONDITIONAL for RANDOM. This option can be used only for DIST=T. See the section Specifying Value Lists in Analysis Statements for information about specifying the keywordlist.
fixed variables
random (bivariate normal) variables
enables fractional input and output for sample sizes. See the section Sample Size Adjustment Options for information about the ramifications of the presence (and absence) of the NFRACTIONAL option.
specifies the number of variables adjusted for in the correlation between the two primary variables. The default value is 0, corresponding to a simple correlation. See the section Specifying Value Lists in Analysis Statements for information about specifying the numberlist.
specifies the sample size or requests a solution for the sample size with a missing value (NTOTAL=.). Values for the sample size must be at least when DIST=T and MODEL=CONDITIONAL, and at least when either DIST=FISHER or when DIST=T and MODEL=UNCONDITIONAL, where is the value of the NPARTIALVARS option. See the section Specifying Value Lists in Analysis Statements for information about specifying the numberlist.
specifies the null value of the correlation. The default value is 0. This option can be used only with the DIST=FISHERZ analysis. See the section Specifying Value Lists in Analysis Statements for information about specifying the numberlist.
controls how the input and default analysis parameters are ordered in the output. OUTPUTORDER=INTERNAL (the default) arranges the parameters in the output according to the following order of their corresponding options:
The OUTPUTORDER=SYNTAX option arranges the parameters in the output in the same order in which their corresponding options are specified in the ONECORR statement. The OUTPUTORDER=REVERSE option arranges the parameters in the output in the reverse of the order in which their corresponding options are specified in the ONECORR statement.
specifies the desired power of the test or requests a solution for the power with a missing value (POWER=.). The power is expressed as a probability, a number between 0 and 1, rather than as a percentage. See the section Specifying Value Lists in Analysis Statements for information about specifying the numberlist.
specifies the number of sides (or tails) and the direction of the statistical test. Valid keywords are
onesided with alternative hypothesis in same direction as effect
twosided
upper onesided with alternative greater than null value
lower onesided with alternative less than null value
The default value is 2.
specifies a test of the Pearson correlation coefficient between two variables, possibly adjusting for other variables. This is the default test option.
This section summarizes the syntax for the common analyses supported in the ONECORR statement.
The following statements demonstrate a power computation for Fisher’s z test for correlation. Default values of TEST=PEARSON, ALPHA=0.05, SIDES=2, and NPARTIALVARS=0 are assumed.
proc power; onecorr dist=fisherz nullcorr = 0.15 corr = 0.35 ntotal = 180 power = .; run;
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