LIFESPAN MEASUREMENTS IN THE MALE RAT
Abstract
Measures of lifespan were determined for a population of male Sprague-Dawley derived male rats, comprised of 747 animals from eighteen experiments. Variations in ln measures among experiments were found even under stable environmental conditions in a single strain of rats with no known epidemic infections. Measures of central tendency and dispersion appeared to be uncorrelated with each other, and normally distributed among experiments. Within most experiments there was a definite tendency for an excess (above the normal distribution) of shorter lifespans, and in seven experiments this resulted in significant deviations from the normal distribution. On a composite basis, the frequency distribution of lifespans, and the associated survival curve, were not those of a normally distributed variate. Consideration of life expectancies at various ages and age specific death rates revealed that the force of mortality declines at advanced ages. These findings indicate the need for caution in selecting statistical procedures for analysis of lifespan information.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 09, 1963
- Accession Number
- AD0409550
Entities
People
- D. C. Jones
- D. J. Kimeldorf
Organizations
- Northwestern University