A pedant writes:
The ratio in question is named after J.P. Mills.
Thus Mills ratio, Mills' ratio and Mills's ratio
are all acceptable as correct renderings. Any use
of the apostrophe is dangerous as it tends to be
copied in the wrong place. So I prefer "Mills"
and this seems to be the commonest correct
rendering in the literature.
But Mill's and mill's are both incorrect renderings.
Nick
n.j.cox@durham.ac.uk
P.S. While I am at it, the correct spelling is
"Stata". This is explained explicitly at the end
of the Statalist FAQ and inadvertently that catches
out people who evidently have not read the FAQ carefully
enough!
Nishant Dass
> I have the following question about Inverse Mill's Ratio:
>
> I run a probit regression for the selection equation and
> want to calculate the inverse mill's ratio.
>
> I found the following formula:
> gen imr = normd(y_hat)/normprob(y_hat)
> where "y_hat" is the fitted value from the probit equation.
>
> I tried searching for "normd" and "normprob" functions to
> see what this formula really does but couldn't find these
> functions in STATA Help.
>
> Could someone please confirm whether this is the correct
> formula for calculating the inverse mill's ratio? Thank
> you very much.
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