Just to add onto Greg's comments, you may want to review this thread over on MedStats, since this topic was just discussed extensively this week, initially as a query about using LOS as a covariate:
http://groups.google.com/group/medstats/browse_thread/thread/f875fdeeaf48dc38?hl=en It is highly unlikely that LOS is normally distributed. HTH, Marc Schwartz On Jul 8, 2011, at 10:43 AM, Greg Snow wrote: > How are you measuring length of stay? A chi-square test suggests that you > have it categorized, a t-test assumes it is continuous (and relatively > symmetric with the amount depending on sample size). > > Do you have any censoring? (patients dying or transferring before discharge) > if so you should look at survival analysis. > > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf Of gwanme...@aol.com > Sent: Friday, July 08, 2011 3:23 AM > To: r-help@r-project.org > Subject: [R] Using t tests > > Dear Sir, > > I am doing some work on a population of patients. About half of them are > admitted into hospital with albumin levels less than 33. The other half have > albumin levels greater than 33, so I stratify them into 2 groups, x and y > respectively. > > I suspect that the average length of stay in hospital for the group of > patients (x) with albumin levels less than 33 is greater than those with > albumin levels greater than 33 (y). > > What command function do I use (assuming that I will be using the chi > square test) to show that the length of stay in hospital of those in group x > is > statistically significantly different from those in group y? > > I look forward to your thoughts. > > Ivo Gwanmesia ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
