For two samples x and y from normal distributions with unknown means and unknown variances, perform an F-test of the null hypothesis of equal variances. Under the null, the test statistic f follows an F-distribution with df_num and df_den degrees of freedom.
With the optional argument string alt, the alternative of interest can be selected. If alt is
"!="or"<>", the null is tested against the two-sided alternativevar (x) != var (y). If alt is">", the one-sided alternativevar (x) > var (y)is used. Similarly for "<", the one-sided alternativevar (x) > var (y)is used. The default is the two-sided case.The p-value of the test is returned in pval.
If no output argument is given, the p-value of the test is displayed.