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Biomedical subjects

D A Sprott

Publications and source records attributed to D A Sprott.

12 recordsLinked to original sources
PubMed1999

Conditional inference for predictive agreement.

We introduce the concept, and a measure of predictive agreement, tau, for two raters classifying items into q categories. The measure is based on the linear combination of log odds ratios from 2 x 2 subtables of a q x q cross-classification table. We show that analysis procedures for this measure, and transforms of it, can be based on conditional likelihood procedures. These procedures are exact, which is particularly helpful because of the small tabular cell frequencies which can typically arise with agreement data. To illustrate the advantages of the methodology, examples of typical agreement data arising from medical studies are considered. We demonstrate that the conditional likelihood function portrays the available sample information about tau, often more appropriately than the maximum likelihood estimate and an associated standard error. We highlight the value of combining information via likelihoods in an example involving 24 2 x 2 tables. An example involving three categories is used to illustrate that the methodology for the overall agreement measure can be adapted to examine relative agreement between pairs of categories.

Alcohol Drinking↗
PubMed1989

Statistical methods for measuring interactions between protectors and sensitizers for freeze-thaw survival data.

A statistical model is developed to generate the survival probabilities of cells subjected to freeze-thaw treatments using various sensitizing and/or protective agents. The purpose is to determine whether different freeze-thaw protective agents act independently or whether there is an interaction between the agents. The model permits a statistical analysis of the data to yield an objective quantitative assessment of the size and nature of the interaction.

Cell Survival↗
PubMed1974

Statistical analysis of data bearing on the number of particles required to form a plaque.

Methods of statistical analysis are presented for one or more dilution series experiments where the quantity of interest is the number of virus particles required to infect a cell. These methods are illustrated on several data sets drawn from the literature. Data from seven series, which have been used to support a two-particle model in the literature, are here shown to reject such a model decisively, whereas fifteen other experiments are found to be in excellent agreement with a one-particle model.

Hemolytic Plaque Technique↗