{* *! version 1.0.4  07jul2010}{...}
{phang}
{opt cpr(a,b)} calculates the conditional probability
Pr(a {ul:<} y {ul:<} b | y > ll), where ll is the truncation point found in
{cmd:e(llopt)}.  The syntax for this option is analogous to that used for
{opt pr(a,b)} except that a must be greater than the truncation point.
