void ftest(double data1[], int n1, double data2[], int n2,
		   double& f, double& prob)
{
	double df1,df2,dum1,dum2,ave1,ave2,var1,var2;
    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;
    }
    dum1 = betai(0.5 * df2, 0.5 * df1, df2 / (df2 + df1 * f));
    dum2 = 1.0 - betai(0.5 * df1, 0.5 * df2, df1 / (df1 + df2 / f));
    prob = dum1 + dum2;
}