# Tom

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```					Methods of Sampling
By Tom B
Different methods of sampling
   Random Sampling
   Stratified Sampling
   Systematic Sampling
   Cluster Sampling
   Quota Sampling
   Convenience Sampling
   Combining Methods.
Random Sampling
   Everything possible item of data has
an equal chance of being used in the
survey.
   Use a random number table
   Use a random number generator or a
scientific calculator
   Put the numbers into a hat
Stratified Sampling
   Divide the population into categories
(strata)
   Male or Female, age, social class,
earnings.
   From within each strata take a
random sample
   The size of each sample is in
proportion to the strata from which it
is taken
Systematic Sampling
   Chosen at regular intervals from an
unordered list
   E.g.Take every 5th student from a
register
   Used when population is very large
   May not always be truly
representative
Cluster Sampling
   The population being sampled is split into
groups, or clusters.
   The clusters to be sampled are randomly
chosen.
   Every cluster is looked at.
   Clusters should be more or less an equal
size
   A large number of clusters is best so that
it minimizes the chances of the sample
being unrepresentative.
   Popular with scientists
Quota Sampling
   Used in market research
   Information is given about the quota or
amount of each section with a certain
characteristic that is to be sampled.
   No sampling frame is required
   Major disadvantage is that the choice of
the sample is the surveyors decision which
can lead to questions of bias.
Convenience Sampling
   This is where the most convenient sample
is chosen.
   For a sample of 50 students from a school
it will simply be that they choose the first
50 names on the register.
   Very quick and is not time consuming
   Major disadvantage is that it can lead to
bias and the sample can be
unrepresentative.
Combining Methods
   Sometimes you have to use more than
one sampling method.
   Opinion polls in politics use combination of
quota and cluster sampling
   A major disadvantage of the conclusions
drawn is that opinions can change
   Each method of sampling has a drawback
you have to choose the right one for what
you need it for.

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 views: 7 posted: 2/21/2012 language: pages: 9
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