Calculates the log of Wilks' lambda statistic
for a given super_sample object.
This function ensures that the within-group
and total covariance matrices are computed,
then computes the difference of their log determinants.
Calculates the log of Wilks' lambda statistic
for a given super_sample object.
This function ensures that the within-group
and total covariance matrices are computed,
then computes the difference of their log determinants.