Re: Bootstrap resampling! -> Randomization test

From: Nick Holford <n.holford@auckland.ac.nz> Subject: Re: Bootstrap resampling! -> Randomization test Date: Fri, 30 Mar 2001 16:56:19 +1200 Steve, You bring up a new phrase "statistical verification". I dont really know what this means. I dont need new phrases. What I need is to be able to make a decision about whether one model is "better" than another. I need this almost every day. In practice I use deltaOBJ. If its bigger than 10 then I am convinced especially if FOCE. It its betwen 4 and 6 I am willing to accept it may be better than the other model especially if the parameters look reasonable. I cannot rely solely on mechanistic or biological plausibility alone. It is plausible that women have a different clearance from men but I need the data to convince me and would rely on deltaOBJ. On the other hand I routinely use an allometric size model for clearance and volume and if the OBJ gets worse when I add this in I still keep the allometric model but then think what other covariate is confounded with weight that is worsening the fit (ignoring the thorny issue of a local minimum). For some special cases I may want to be more concerned about how to achieve a certain alpha level and then the randomization test offers the means to figure it out. Given the run times it is certainly not something one can apply to every model building hypothesis. Nick -- 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.phm.auckland.ac.nz/Staff/NHolford/nholford.htm