6. SAMPLING
According to W.G.Cochran, “In every
branch of science we lack the resources
to study more than a fragment of the
phenomena that might advance our
knowledge”.
7. Bases of Sampling
Underlying Homogeneity amidst
complexity
Possibility of representative selection
Absolute accuracy not essential
8.
9.
10.
11.
12. SIMPLE RANDOM SAMPLING
Most popular sampling technique.
It is the basis for other types of
probability sampling.
Selection of an item is no way dependent
upon the selection of any other items.
Eg: coin tossing , lot, dice throwing
13.
14. SYSTEMATIC SAMPLING
Systematic sampling involves
selecting every kth item of the
population.
Eg:If 4% of the sample is desired
K=100/4=25(N/n)
1st element –randomly &other
elements at equal interval.
15.
16. SYSTEMATIC RANDOM SAMPLE
STEPS
Number the units in the population from 1 to N
Decide on the n (sample size) that you want or
need
K = N/n = the interval size
Randomly select an integer between 1 to k
Then take every kth unit
17.
18.
19. STRATIFIED RANDOM
SAMPLING
A sample is drawn from each
“stratum” at random
Two types of this sampling
proportionate sampling
disproportionate sampling
20. PROPORTIONATE SAMPLING
The number of units to be drawn from each
stratum is the same proportionate they
constitite in the universe.
Eg:
N1 =4000, N2=2400, N3=1600
n-sample to be selection
p1=N1/N=1/2,n1=np1=30*1/2=15
21. DISPROPORTIONATE
SAMPLING
An equal number of cases are taken from each
stratum regardless of the size of the strata in
proportion to the universe.
If the purpose of research study happens to be
to compare the differences among the strata,
then equal sample selection from each stratum
would be more efficient even if the strata differ
in sizes.
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23.
24. MULTIPLE SAMPLING
At every stage /level sampling is
done at random
We can make the random sampling
either simple or stratified at every
stage.
25.
26.
27. DOUBLE SAMPLING
It is a two phase sampling techniques.
In this techniques a large preliminary
sample is drawn and the second sample is
taken as a such sample of the first
sample.
This two stage sampling is really a matter
of sampling with in samples.
28. CLUSTER SAMPLING
We first sample group & then individuals from
the groups selected .
If we sample groups first and then include all
in the sample.
When the population is broken into
geographical areas that constitute the primary
sample units , then the sample is called “Area
sample”.
29.
30. CLUSTER SAMPLING STEPS
Divide population into clusters (usually along
geographic boundaries)
Randomly sample clusters
Measure all units within sampled clusters
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32.
33.
34. JUDGEMENT SAMPLING
If for any reason in the researcher ‘s
judgement a particular subgroup or
stratum is satisfactorily representative
of the population its selection illustrates
the principles of judgement sampling.
He purposely selects a group leaving
out members of all other groups in the
population.
35.
36. QUOTA SAMPLING
Quota sampling is the technique that
combines judgement and probability.
It is essentially a stratified sample
but the proportion of population
under each stratum is decided on
judgement and the quota is fixed.
37.
38. INCIDENTAL SAMPLING
Incidental or some times called
accidental sampling is appicable
when such groups used as sample are
easily or readily available.
Eg:children in a school.
39. CONVIENCE SAMPLING
It is generally known as careless , un
systematic , accidental or opportunistic
sampling.
The sample is selected according to the
convenience of the researcher.
He selects certain units convenient to
him.
43. CONCLUSION
It can be said that using a sample
in research saves in mainly on
money and time , if a suitable
sampling and research method to
research process in well done.
