Hi everyone,

In social reseach, economic and others fields "Non-Equivalent Groups Analysis" shows an issue when data are biased between Posttest and Pretest. Many authors talk about the Regression-Discontinuity Analysis wich is used when dispersion are different in both groups (in this case Control vs. Treatment). I have found this function that seems to work well finding this problem (sm.discontinuity), also fixing this problem in is not trivial among reseachers.

A good source of theorical information correcting this problem can be found here: http://www.socialresearchmethods.net/kb/statnegd.php

Someone knows if there's any way to do this through R?

Thanks in advance!
José
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