Sampling error in statistics can be defined as
the errors which arise due to unrepresentativeness of a sample from
a population. It is one type of statistical error which occurs when
an analyst does not select a sample that represents the
population.
Sampling error is unavoidable, but they can be reduced. There
are two ways to reduce sampling error:
- By Increasing sample size: Sampling error and
the sample size are negatively correlated. That means if sample
size increases, sampling error decreases and vice versa. If the
sample size = population size, then sampling error will be null(But
this situation is not practical).This is because as sample size
increases ,the sample gets closer to the population, and thereby
decreases the potential for deviations from the actual
population.
- By stratification: For a population containing
similar elements simple random sample is a good representative of
the population. But for a population containing dissimilar
elements, to improve the result of the sample, the design needs to
be modified. The population is to be divided in different subgroups
(strata) containing similar elements. From each
strata (called stratum), a sub sample is selected
at random. In this way all groups are represented in the sample and
the sampling error is reduced.
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