Population Estimation. Objective : To estimate from a sample of households the numbers of animals in a population and to provide a measure of precision for the estimate.
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Objective : To estimate from a sample of households the numbers of
animals in a population and to provide a measure of
precision for the estimate.
Assumption : Units in the population are selected at random.
Population : For our purposes we can consider this to be the animals
in a P.A. or the animals in a woreda. Estimation of
population numbers at the zone level is more
problematic since the selection of woredas was
representative, not random.
Definitions
Population The animals in a P.A., in a woreda or in a zone.
Total The total number of animals in the population.
Mean The average number of cattle owned per household in
the population.
Variance A measure of the variation in numbers of cattle owned by
different households in the population.
Standard error The precision with which the total number of animals is estimated. The standard error is calculated from the variance.
Random sample of household in a P.A.
s2 = Sum (y – m)2/ (n –1)
[ N(N  n)s2/ n ]
±

2
Nm
N(N
n)s
/n
where summation is over strata.
2
±

Sum
Nm
Sum
[
N(N
n)s
/n
]
5355 – 2 x 342 to 5355 + 2 x 342
or 4671 to 6039 cattle
with a 95% chance of being correct.
Question 1. Is this range reasonable or unreasonable?
Question 2. How can we reduce the range?
Improving the precision of population estimation at the woreda level