Min-Young-<div><br></div><div>Thanks for your interest in using our package. </div><div><br></div><div>We have not yet implemented duration models into our package. In principle it should be able to handle these but we have not yet done this. If you know some R you can modify our code. Otherwise this will have to wait until a future release.</div>
<div><br></div><div>One quick note, in our framework you need only two models (using your notation, Y=M+X and M=X).</div><div><br></div><div>best,</div><div>Dustin</div><div><br clear="all">Dustin Tingley<br>Government Department<br>
Harvard University<br><a href="http://scholar.harvard.edu/dtingley" target="_blank">http://scholar.harvard.edu/dtingley</a><br><br>
<br><br><div class="gmail_quote">On Mon, Oct 3, 2011 at 1:48 PM, Min-Young Kim <span dir="ltr"><<a href="mailto:mkim.uiuc@gmail.com">mkim.uiuc@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div lang="KO" link="blue" vlink="purple"><div><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Dear Professor Dustin Tingley,<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">I am writing this email to ask you a question on the “Causal Mediation Analysis Using R”.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">I am a PhD candidate at the business school of the University of Illinois at Urbana-Champaign. <u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">I am currently working on a project in which I employ a mediation analysis. But I am facing some difficulties due to the nature of my mediating variable.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">The following is a brief outline of the mediation model.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>1.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">X: a count variable (the number of countries)<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>2.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">M: time (time taken to first forward citation in patent citation network)<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>3.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Y: a count variable (the number of citations a patent receives)<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Due to the various data types, I am estimating with:<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>1.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">A negative binomial model for X->Y<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>2.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">An accelerated-failure time (AFT) model (one of the survival models) for X->M<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>3.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">A negative binomial model for M->Y<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">As many of the current statistical models for mediating analyses are developed for continues mediating and/or dependent variables, I am experiencing difficult time in testing my hypotheses.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">In the meantime, I have found that “A Question on Causal Mediation Analysis Using R” could help me dealing with these issues.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">But when reading through the instruction manual, especially Table 1 in page 9 (of the version September 19, 2011), I found that that accelerated-failure time model is not included in the mediator model type.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">So, my question is:<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>1.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Whether it is possible to test my mediation hypotheses with your “mediate” program for R?<u></u><u></u></span></p>
<p style="margin-left:38.0pt"><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><span>2.<span style="font:7.0pt "Times New Roman""> </span></span></span><u></u><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">if not, do you have any plan to include the AFT model in the “mediate” program?<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Any comments would be really appreciated.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Thank you so much.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Sincerely yours,<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p><font color="#888888"><p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D">Min-Young Kim<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Cambria","serif";color:#1F497D"><u></u> <u></u></span></p></font></div></div></blockquote></div><br></div>