nbsp;&nbsp;&nbsp;veh.control &lt;- beta[2] - beta[1] <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;test.sub &lt;- beta[3] - beta[1]<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;pos.control &lt;- beta[4] - beta[1]<br>&nbsp;&nbsp;&nbsp;}
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</font><font face="Arial" color="#000100" size="3"><br>We note a number of tricks in setting up this model. First, individuals who are censored are given a missing value in the