[R] Using t tests

[Marc Schwartz]

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-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Gwanmesia at aol.com
> Sent: Friday, July 08, 2011 3:23 AM
> To: r-help at 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