[R] Ellipse that Contains 95% of the Observed Data

[Bert Gunter]

Easy. See below.

Bert Gunter
Genentech Nonclinical Biostatistics
 
 -----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Tom La Bone
Sent: Monday, March 29, 2010 6:56 AM
To: r-help at r-project.org
Subject: Re: [R] Ellipse that Contains 95% of the Observed Data


Concisely, here is what I am trying to do:

#I take a random sample of 300 measurements. After I have the measurements 
#I post stratify them to 80 type A measurements and 220 type B measurements.

#These measurements tend to be lognormally distributed so I fit them to 
#determine the geometric mean and geometric standard deviation of each
stratum. 
#The question is: are the geometric mean and geometric standard deviation of

#the type A measurements the same as the geometric mean and geometric 
#standard deviation of the type B measurements?

-- No.

(So you probably need to 

1. Ask a more statistically meaningful question.

2. Get a MUCH larger sample (you're talking about bivariate sd's here!!)

)

-- Bert