Not enough sex!

From:Nick Holford Subject: [NMusers] Not enough sex! Date:Wed, 31 Jul 2002 07:57:24 +1200 {assuming the subject line got past your spam filter...] I forgot to say that just simulating sex once is not enough. Ideally you should simulate sex about 6 times i.e. simulate the missing SEX covariate in 6 different data sets and run your model with each of these data sets then average the parameter estimates you get across all the 6 runs. This is called multiple imputation. Why 6 times? This is Rubin's Rule (Don Rubin is Prof Statistics at Harvard and invented the multiple imputation method). In this particular instance the rule of 6 is even older -- the Romans would say SEX was enough too. The joint function model (which I mention below) gets around the need to have 6 data sets so is probably more time efficient in the long run. Nick Holford, Divn Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x6730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/