Another method would be to use a summary that incorporates both as a
measure of obesity, In medical investigations it is common to use the
BMI which is the ratio of (weight in Kg) to (height in meters squared).
Yet a third method would be to investigate for nonlinearity on the
response function using splines in the model. I have not yet seen
evidence of collinearity offered, so creating the full model as Simon
suggests might be a first step. Much will depend on the quantity of
data. If you only have 100 observations there will be severe
limitations on the options.
--
David Winsemius
On Mar 12, 2009, at 2:37 AM, Simon Blomberg wrote:
You only have one response variable, so MANOVA is not appropriate. One
option would be to compare BP ~ Weight + Height with BP ~ 1. That
would
give you a joint test of weight and height together. Since they are
collinear, that should tell you the overall effect of "size". There
are
other options, most of which involve discarding some of the data.
Frank
Harrell's book is a font of wisdom on this sort of thing.
Harrell, F. E., Jr. (2001). Regression Modeling Strategies. Springer.
Simon.
On Thu, 2009-03-12 at 00:20 -0600, Ding Xiao wrote:
Hi All,
I have questions about MANOVA which I am still not sure if
appropriately I should use it.
For example I have a data set like this:
BloodPressure (BP) Weight Height
120 115 165
125 145 198
156 99 176
I know that BloodPressure is correlated with both Weight and
Height, however colinearity exists between Weight and Height. When
I use BP = Weight + Height as the model, one is got to be
insignificant. I was trying to use a BP + Weight = Height model,
but not sure how to use it.
Should I use MANOVA? or I just have to do two equations as BP =
Weight & Weight = Height
Any suggestions and answers are greatly appreciated!
Ding
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--
Simon Blomberg, BSc (Hons), PhD, MAppStat.
Lecturer and Consultant Statistician
School of Biological Sciences
The University of Queensland
St. Lucia Queensland 4072
Australia
Room 320 Goddard Building (8)
T: +61 7 3365 2506
http://www.uq.edu.au/~uqsblomb
email: S.Blomberg1_at_uq.edu.au
Policies:
1. I will NOT analyse your data for you.
2. Your deadline is your problem.
The combination of some data and an aching desire for
an answer does not ensure that a reasonable answer can
be extracted from a given body of data. - John Tukey.
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
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