Thall and Vail (1990) presented longitudinal data from a clinical trial of 59 epileptics, who were randomized to a new drug or a placebo (T=0 or T=1). Baseline data were available at the start of the trial; the trial included the logarithm of the average number of epileptic seizures recorded in the 8-week period preceding the trial (B), the logarithm of age (A), and visit (V: a linear trend, coded (-3,-1,1,3)/10). A multivariate response variable (y) consists of the seizure counts during 2-week periods before each of four visits to the clinic.
A data frame with 236 observations of the following 7 variables.
The seizure counts during 2-week periods before each of four visits to the clinic.
Treatment(0=new drug, 1=placebo).
The average number of epileptic seizures in the 8-week period preceding the trial.
The logarithm of age (in years) of each patient.
Linear trend coded (-3, -1, 1, 3)/10 for four visits of each patient.
Patient number for 59 epileptics.
Observation number for 236 observations.
Thall, P. F. and Vail, S. C. (1990). Some covariance models for longitudinal count data with overdispersion, Biometrics 46, 657–671.
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