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<head><title>Brewing with Rapache: useR2007 example with Hmisc</title>
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<h2>Power and Sample Size Calculations with spower from Hmisc</h2>
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<p>The following example<b>[1]</b> demonstrates the flexibility of spower and
related functions from <b><a href="http://biostat.mc.vanderbilt.edu/twiki/bin/view/Main/Hmisc">Hmisc</a></b>. We simulate a 2-arm (350 subjects/arm) 5-year follow-up
study for wich the control group's survival distribution is Weibull with 1-year
survival of .95 and 3-year survival of .7. All subjects are followed at least
one year, and patients enter the study with linearly increasing probability
starting with zero. Assume (1) there is no chance of dropin for the first 6
months, then the probability increases linearly up to .15 at 5 years; (2) there
is a linearly increasing chance of dropout up to .3 at 5 years; and (3) the
treatment has no effect for the first 9 months, then it has a constant effect
(hazard ratio of .75).
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[1] Alzola CF, Harrell FE:  <a href="http://biostat.mc.vanderbilt.edu/twiki/pub/Main/RS/sintro.pdf">An Introduction to S and the Hmisc and Design Libraries</a>. Freely available electronic book.
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	<label>Web site created by:</label>
	<a href="http://biostat.mc.vanderbilt.edu/JeffreyHorner">Jeffrey Horner</a><br>
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	<label>With the following software:</label>
	<a href="http://biostat.mc.vanderbilt.edu/Hmisc">Hmisc</a><br>
	<a href="http://www.rforge.net/brew/">brew</a><br>
	<a href="http://www.rforge.net/Cairo/">Cairo</a><br>
	<a href="http://biostat.mc.vanderbilt.edu/rapache/">rapache</a><br>
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<div id="plot"><% brew('useR2007plot.rhtml') %></div>
Characteristics of control and intervention groups with a lag in the treatment effect and with non-compliance in two directions.
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<form method="get" name="spower" action="#">
<div class="clearfix"><label>1-year Survival Rate:</label><input type="text" name="p1" value="<%=p1%>"></input></div>
<div class="clearfix"><label>3-year Survival Rate:</label><input type="text" name="p2" value="<%=p2%>"></input>
<div class="clearfix"><label>Treatment Effect Start Month:</label><input type="text" name="mo" value="<%=mo%>"></input>
<input type="button" onclick="RePlot()" value="Re-plot"></input></div>
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<input type="button" onclick="ReSimulate()" value="Power Estimate:"></input>
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<div id="spowerResult"></div>
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