st: New package -rtmci- is available for download from SSC

["Ariel Linden" <ariel.linden@gmail.com>]

Thanks to Kit Baum (and on Christmas no less), a new package -rtmci- is
available for download from SSC (ssc describe rtmci)

-rtmci- calculates the regression to the mean (RTM) effect for a variable
that is generally measured at two points in time (i.e., "pre-test" and
"post-test"), based on a defined cutoff value on the "pre-test" measure, and
estimates confidence intervals using bootstrap simulation. 

Regression to the mean, originally termed "regression toward mediocrity",
was described over a century ago by Sir Francis Galton upon discovering that
on average, tall parents had children shorter themselves and short parents
had taller children. 

RTM poses a major threat to the internal validity of any study in which
subjects are initially selected for their extreme values. Upon
remeasurement, the sample mean from this outlier group is likely to be much
closer to the overall population mean. This statistical phenomenon can be
easily confused with a
treatment effect.

If only summary level statistics are available (e.g., as published in a
journal article), the user may consider using -rtmcii-, an immediate form of
-rtmci-.

Stata 11.0 is required.

I hope this program will prove helpful!

Ariel


*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/