snails                 package:MASS                 R Documentation

Snail Mortality Data

Description:

     Groups of 20 snails were held for periods of 1, 2, 3 or 4 weeks in
     carefully controlled conditions of temperature and relative
     humidity.  There were two species of snail, A and B, and the
     experiment was designed as a 4 by 3 by 4 by 2 completely
     randomized design.  At the end of the exposure time the snails
     were tested to see if they had survived; the process itself is
     fatal for the animals.  The object of the exercise was to model
     the probability of survival in terms of the stimulus variables,
     and in particular to test for differences between species.

     The data are unusual in that in most cases fatalities during the
     experiment were fairly small.

Usage:

     data(snails)

Format:

     The data frame contains the following components:

     'Species' Snail species A (1) or B (2)

     'Exposure' Exposure in weeks

     'Rel.Hum' Relative humidity (4 levels)

     'Temp' Temperature, in degrees Celsius (3 levels)

     'Deaths' Number of deaths

     'N' Number of snails exposed

Source:

     Zoology Department, The University of Adelaide.

References:

     Venables, W. N. and Ripley, B. D. (1999) _Modern Applied
     Statistics with S-PLUS._ Third Edition. Springer.

