For public health purposes, the force of mortality in a population is usually measured by means of such indices as crude death rate. Infant mortality rate, specific death rate at different ages by sex, etc another effective and at the same time comprehensive method of describing mortality in a population is by means of life tables. A life table is composed of several sets of values showing how a grownup of infants all supposed to be born at the same time and experiencing unchanging mortality conditions would gradually die out. In other words, the life table is a convenient method for summarizing the mortality experience of any populating group-that is it provides concise measures of the longevity of the population. Such tables are usually worked out after each decennial census to represent mortality conditions either during the previous decennium or during shorter periods covering the date of the census separate tables for males and females are usually prepared. For detailed subdivision of a country or different population segments. A life table can also be constructed to show how a group of babies would die if. Hypothetically, one or more causes of data were eliminated. In recent years life table techniques are being increasingly applied to follow up studies of chronic diseases or hospital patients.
Illustration:- the table below gives the life table for rabbits, find d2, p1 q2, L3,
| X |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
| Lx |
100 |
90 |
80 |
75 |
60 |
30 |
0 |
Solution:-
dx = lx - lx +1
dx = 80 - 75 = 5
qx = dx / lx = lx - lx +1 / lx
qx = 100 - 90 /100 = 10 / 100 = 0.1
Px = 1 - qx = 1 - dx / lx
P1 = 1 - qx / lx =1 - h - li +1
= 1 - 90 - 80 / 90 = 0.89
X = lx - dx / 2
l2 = l2 - d3 / 2 =l 3 - l3 - l3 + 1 / 2
= 75 - 75 - 60 / 2 = 67.5
ex = 2px + pxex
ex - px ex = 2px
ex (1 - px) = 2px
ex = 2px / 1-px e4 = 2p4 / 1- p4
P4 = 1 - q4 = 1 - l4 - l4 + 1 / l2
=1 - 60 - 30 / 60 = 0.5
e4 = 2 x 0.5 / 1 - 0.5 = 1.0 / 05 = 2
e4x = e4 + 1 / 2 = 2 + 1/ 2 = 2.5
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