Tracking procedures in follow-up studies of drug abusers.

One of the problems that researchers frequently confront is the tracking and locating of research subjects. "Deviant" populations may present special difficulties in this regard. The experiences of a trained field survey unit doing drug-related research are examined.

Statistical analysis of the bioassay of continuous carcinogens.

In an experiment consisting of the continuous constant application of various carcinogenic regimens to a pure strain of experimental animals for a long period, the cancer incidence rates so caused may be studied and compared by the fit of an appropriate class of statistical distributions. In this paper we show that a Weibull distribution in which the age-specific cancer incidence rate rises as a power of time since first risk is more appropriate than a lognormal distribution. If the Weibull family of distributions is used, more information can be extracted from the data, and differences of toxicity between various regimens will not bias the comparison of their carcinogenic forces.