ftest.c

Numerical Recipes 是国际公认的高水平的、关于数值计算的书

void ftest(data1,n1,data2,n2,f,prob)
float data1[],data2[],*f,*prob;
int n1,n2;
{
	float var1,var2,ave1,ave2,df1,df2;
	void avevar();
	float betai();

	avevar(data1,n1,&ave1,&var1);
	avevar(data2,n2,&ave2,&var2);
	if (var1 > var2) {
		*f=var1/var2;
		df1=n1-1;
		df2=n2-1;
	} else {
		*f=var2/var1;
		df1=n2-1;
		df2=n1-1;
	}
	*prob = 2.0*betai(0.5*df2,0.5*df1,df2/(df2+df1*(*f)));
	if (*prob > 1.0) *prob=2.0-*prob;
}