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Survivorship function

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Survivorship function  (SURVIVORSHIP function)

The course of mortality throughout life may be described by a mortality table1 or life table1. This consists of one or more life table functions2, all of which are mathematically related and may generally be derived when the value of one of them is known. The survivorship function3 shows the number of survivors4 of a cohort (116-2) of births to exact age x, on the assumption that the cohort is subjected to the rates of mortality shown. The number of births in the original cohort is known as the radix5 or root5 of the life table and the process of diminution is known as attrition6. From a knowledge of the survivorship function it is possible to compute the probability of survival7 from exact age x to exact age x+ n.

  • 4. The number of survivors to exact age x is denoted by lx.
  • 7. The probability of survival from age x to age x + n is always written npx and from age x to age x + 1: px.