cholesterol: Serum cholesterol from the National Cooperative Gallstone...
In ALA: Data sets and examples for the book "Applied Longitudinal Analysis"

Description Usage Format Details Note Source References Examples

The data are from the National Cooperative Gallstone Study (NCGS), where one of the major interests was to study the safety of the drug chenodiol for the treatment of cholesterol gallstones.

1	data(cholesterol)

A data frame with 515 observations on the following 4 variables.

id: a factor with 65 levels
treatment: a factor with levels placebo and chenodiol
month: a numeric vector
cholesterol: a numeric vector

In this study, patients were randomly assigned to high-dose (750 mg per day), low-dose (375 mg per day), or placebo. This dataset consists of a subset of data on patients who had floating gallstones and who were assigned to the high-dose and placebo groups. In the NCGS it was suggested that chenodiol would dissolve gallstones but in doing so might increase levels of serum cholesterol. As a result, serum cholesterol (mg/dL) was measured at baseline and at 6, 12, 20, and 24 months of follow-up. Many cholesterol measurements are missing because of missed visits, laboratory specimens were lost or inadequate, or patient follow-up was terminated.

Original variable names have been adapted to R conventions. Data were reshaped from wide to long format and the response named cholesterol.

http://biosun1.harvard.edu/~fitzmaur/ala

Wei LJ, Lachin JM (1984) Two-Sample Asymptotically Distribution-Free Tests for Incomplete Multivariate Observations. Journal of the American Statistical Association 79:653-661.