〔例2-17〕在一项某中药治疗感染性腹泻的III 临床试验中,设计安排3 种干预,即高剂量药物组、低剂量药物组和安慰剂组,主要疗效指标为愈显率。根据
II 期临床试验数据,3个组的愈显率分别为60%、50%和40%,试以平衡设计、双侧检验水准0. 05、检验效能90%估计最低样本量。
SAS9. 2 软件实现:
%macro PGT0( p,v,alpha,g,power) ;
data PGT0;
g = &g;
p1 = 0. 6;
p2 = 0. 5;
p3 = 0. 4;
alpha = α
power = &power;
if &p = . then p = ( p1+ p2 + p3) /3;
else p = &p;
if &v = . then v = ( (p1-p) **2 + ( p2-p) **2 + ( p3-p) **2) /g;
else v = &v;
h = v /( p* ( 1-p) ) ;
n = 0;
do until( abs( p1-power) < = 0. 001) ;
p1 = 1-cdf ( 'CHISQUARE',cinv (1-alpha,g-1) ,g-1,g * n* h) ;
end;
n = n + 1;
p1 = 0. 6;
run;
proc print data = PGT0 label;
var alpha p1 p2 p3 g power n;
label alpha = 'Test significance level'
p1 = 'proportion1'
p2 = 'proportion2'
p3 = 'proportion3'
power = 'Power'
n = 'n';
quit;
%mend PGT0;
%PGT0( p = . ,v = . ,alpha = 0. 05,g = 3,power =0. 90) ;