Documentation for carot.dat

Before doing large scale clinical trials, it is important to understand
the pharmacokinetics of a drug. Hence, phase II prevention trials often
administer a drug in various doses to volunteers, and pertinent plasma
levels are then measured at regular intervals. Of particular interest
is how dose level affects the build up of drug in the plasma over
time, as well as how the dose level might affect other blood chemistries.
The data set we will be analyzing for the next couple of weeks arises from
pharmacokinetic studies of beta-carotene.

Forty-six (46) volunteers were randomly assigned to receive one of five
doses of beta-carotene (0,15,30,45, or 60 mg/day) for 9 months in a
double blind fashion. The specific aim of this study was to
determine how different dose levels affected the serum beta-carotene
levels after 3 months and after 9 months. In addition
to measuring the plasma concentration of beta-carotene by dose, we
were also interested in examining whether there was any effect 
of beta-carotene supplementation on vitamin E levels in the plasma.
Because both beta-carotene and vitamin E
are lipid soluble (that is, they are dissolved in fats rather than water),
it might be possible that increased levels of beta-carotene might
affect vitamin E levels in the blood. Other measured variables available
in this data set include subject age, sex, weight, body mass index,
percent body fat, and serum cholesterol level at baseline.

Serum beta-carotene and vitamin E levels are available at baseline
(randomization), after three months, and after nine months. In addition,
a time average (area under the curve to pharmacologists) of those
levels is also available.

The data in carot.dat contains selected data from this clinical trial.
(I have considerably reduced the size of the data set to obtain the 
following variables.) The file is in ASCII format.


PTID   = patient ID
AGE    = subject age at randomization
MALE   = indicator that subject is male
WT     = subject weight at randomization
BMI    = subject body mass index (relates weight to height)
CHOL   = subject serum cholesterol at randomization
PCTFAT = percent body fat at randomization
DOSE   = dose of beta-carotene
CAROT0 = serum beta-carotene at randomization
CAROT1 = serum beta-carotene after three months of treatment
CAROT3 = serum beta-carotene after nine months of treatment
CAUC   = time average of serum beta-carotene while on 
         treatment (area under curve)
VITE0  = serum vitamin E at randomization
VITE1  = serum vitamin E after three months of treatment
VITE3  = serum vitamin E after nine months of treatment
VAUC   = time average of serum vitamin E treatment (area under curve)