Research
methodology
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Example
: Weight measured in kilograms, height in cms., etc.
6.6 Sampling
What is sampling?
Sampling involves the selection of a number of study units from a defined study population.
The population is too large for us to consider collecting information from all its members.
Instead we select a sample of individuals hoping that the sample
is representative of the
population.
When taking a sample, we will be confronted with the following questions:
a) What is the group of people from which we want to draw a sample?
b) How many people do we need in our sample?
c) How will these people be selected?
Definitions
Target population (reference population):
Is that population about which an
investigator wishes to draw a conclusion.
Study population (population sampled):
Population from
which the sample actually
was drawn and about which a conclusion can be made.
For Practical reasons the
study population is often more limited than the target population. In some
instances, the target population and the population sampled are identical.
Sampling unit:
The unit of selection in the sampling process. For example, in a
sample of districts, the
sampling unit is a district; in a sample of persons, a person,
etc.
Study unit:
The unit on which the observations will be collected. For example,
persons in
a study of disease prevalence, or households, in a study of family size.
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