In 1(c), we report only a point estimate, right? 1(d) Anyone know how to do two qqplot's on the same graphs? Like in page 34 of http://gking.harvard.edu/g2001syl/files/cfMP.pdf par(new = T) leaves a lot to be desired - some analogue of the points or lines or abline commands would be nice... 1(e) More seriously, setting "cond=T" in setx (which seems like the right thing to do for the assignment, right?) causes two problems with sim. First, it gives this warning "First Differences are not calculated in conditional prediction models." (So I guess I do the FD by hand?) Second, it starts using enormous amounts of memory, which causes R to crash on my computer. I guess I could use the icegov servers, but presumably there's something more fundamental that I'm missing here, since 20,000 observations shouldn't need more than 1GB of memory... The command that fails for me is: sim(zm.phone, x=setx(zm.phone, phone=0, data = dp, cond=T), x1=setx(zm.phone, phone=1, data = dp, cond=T)) dp is created with m.prop = matchit(phone.contact ~ democrat*age*household*vote96, data = dp, method = "nearest") dp.prop = match.data(m.prop, group="all") dp is the data restricted to mail and door=0. thanks! aram