Erratum
After publication of the original article [1], it came to the authors’ attention that there was an error in the Testing for the existence of a threshold sub-section of the Methods.
Two formulae originally published in this sub-section were incorrect; the correct expressions are the negatives of the expressions published. The formulae should have appeared as follows:
$$ \mathrm{D} = 2\mathrm{l}\left(\mathrm{a},\mathrm{b},\uptau \right)\ \hbox{--}\ 2\mathrm{l}\left({\mathrm{a}}^{'}\right) $$
and
$$ \mathrm{D}' = 2\mathrm{l}\left(\mathrm{a},\mathrm{b},\uptau \right)\ \hbox{--}\ 2\mathrm{l}\left(\mathrm{a}'\right)\ \mathrm{f}\mathrm{o}\mathrm{r}\ \mathrm{a} > \mathrm{b}. $$
