{{{
DATA LIST free
/alpha mdiff sd rho power. 
BEGIN DATA. 
.10 2.0 4.0 0.75 0.90
.10 2.0 4.0 0.5 0.90
END DATA. 

define pairt ( !pos !tokens(1)
                   /!pos !tokens(1)
                   /!pos !tokens(1)
                  /!pos !tokens(1)
                  /!pos !tokens(1)).

COMPUTE #POW = !5.

compute #conf = (1-!1/2).
compute #lc3 = 1.
compute #ind=0.
compute n = 3.000.
comment COMPUTE #LC1 = 10.000.
COMPUTE #CUMF2 = 1 - NCDF.T(IDF.T(#conf,N+N-2),N+N-2,(!2)/SQRT((2*!3*!3/N)*(1-!4))).
COMPUTE #DIFF = 1 .
SET MXLOOPS=10000.
LOOP IF (#DIFF GT .00005) .
+	DO IF (#CUMF2 LT #pow) .
+		COMPUTE #LC3 = N .
+		COMPUTE N = (N + rnd(1)).
+		COMPUTE #CUMF2 =  1 - NCDF.T(IDF.T(#conf,N+N-2),N+N-2,(!2)/SQRT((2*!3*!3/N)*(1-!4))).
+	ELSE .
+		COMPUTE #LC1 = n .
+		COMPUTE n = (n + #LC3)/2 .
+		COMPUTE #CUMF2 = 1 - NCDF.T(IDF.T(#conf,N+N-2),N+N-2,(!2)/SQRT((2*!3*!3/N)*(1-!4))).
+	END IF .
+	COMPUTE #DIFF = ABS(#CUMF2 - #pow) .
END LOOP .
if (n-trunc(n) gt 0.5) #ind=1.
if (#ind eq 0) n=trunc(n)+1.
if (#ind eq 1) n=rnd(n).
EXECUTE .
compute alpha=!1.
compute mdiff=!2.
compute sd=!3.
compute rho=!4.
compute power=!5.
formats n (f7.0) alpha (f5.2) mdiff (f5.2) sd (f5.2) rho (f5.2) power (f5.2).
variable labels n 'Sample Sizes Required' /alpha 'Alpha' /mdiff 'Mean Difference' /sd 'SD' /rho 'Correlation' /power 'Power'.
report format=list automatic align(center)
  /variables=n alpha mdiff sd rho power 
  /title "Paired t-test sample size for given power" .
!enddefine.
matrix.
get m /variables=alpha mdiff sd rho power  /missing=omit.
compute alpha=make(1,1,0).
compute mdiff=make(1,1,0).
compute sd=make(1,1,0).
compute power=make(1,1,0).
compute rho=make(1,1,0).
compute alpha=m(:,1).
compute mdiff=m(:,2).
compute sd=m(:,3).
compute rho=m(:,4).  
compute power=m(:,5).
end matrix.
pairt alpha mdiff sd rho power.
}}}