st: Update of khb on SSC

[Ulrich Kohler <kohler@wzb.eu>]

<>

Courtesy of Kit Baum, an update of the user written program -khb- is
available on SSC. Users of the program can update their installation
with

. adoupdate khb, update

Those who want to install -khb- fir the first time should use


. ssc install khb

instead. 


-khb- implements the Karlson/Holm/Breen method for decomposing
coefficients from non-linear probability models (logit, probit, ...)
into direct and indirect effects.

The update is an added a -bootstrap-/-permute- compatibility mode to
solve a problem that recently came up on Statalist. It is now possible
to do something like this:

. sysuse auto
. bootstrap _b[indirect], reps(50): khb regress mpg length || weight
. permute mpg _b[indirect],  reps(50): khb regress mpg length || weight
 
The update also fixes a bug with that appeared if options
 -xstandard-/-zstandard- are requeseted toghether with weights.

Uli


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