These are notes covering all of Year 1 Statistics. They include key concepts and use examples to solidify the content. These notes helped me achieve an A*.
, Sampling
RandomSampling
....
Give number to each population member , from full list of the
·
a a
population
Generate list of random numbers
·
a
Match these numbers the members select
to
population to
your sample
·
Advantages member of the population has an equal chance
-
Every
of beingbe selected ,
so it's
completed unbiased
Disadvantages -
It can inconvenient if the
population is spread over a
large area it
might be difficult to track down
selected members
Systematic sampling. ..
Give number to each population member from full list of
·
a a
,
the population
Calculate regular internal to by dividing the
population
·
a use
size
by the sample size
that is less than
Generate random
starting point equal to the
·
a
The member of the population is
Six of the interval .
corresponding
the first member of
your sample Keep .
adding the internal to the
starting point to select
your sample
Advantages -
It can be used
for quality control on a
productions a
machine can be set to
up sample every n items . It should
also unbiased sample
give an
Disadvantages The interval could coincide with pattern which
-
regular a
could lead to kids
Opportunity Sampling. ..
·
A
sample is chosen from a section of the population at a
particular
, place and time whatever is convenient for the sampler
Advantages -
Data can be gathered very quickly and
easily
Disadvantages It isn't random and be biased the
very
-
can as
sampler choses which sections of the population
to sample
Sampling....
Stratified
·
Divide the population into categories
·
Calculate thetotal population
Calculate number needed for each in the sample using
:
category
·
Size ofcategor=
y Sireofcategoryinpopulation x total is
sampl
Select the sample for each random
category at
·
the divided up into distinct
Advantages If -
population can be
categories ,
it's
likely to
give a representative sample
. Its
useful when results
may very depending obvious
category
on
Disadvantages It's not useful when there aren't categories
any
.
It can also be expensive because of the extra detail
involved
Quota
Sampling...
Divide the population into
categories
·
·
Give each
category a
quota (number of members to sample)
·
Collect data until the quotas are met in all categories
Advantages- It can be done when there isn't
of the a
full list
population
.
Every sample member member responds because
the interviewer continues to sample until all
quotas are met
Disadvantages - It can be
easily based by the interviewer
,
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