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Unit-12: Sampling

(ii) size of units must be approximately same notes
(iii) each unit must be independent of each other
(iv) each unit must be accessible to the researcher.
(v) selected unit should neither be left nor should it be replaced.

2. Purposive Sampling

When researcher, keeping a purpose before him, knowingly selects few units, it is called purposive
or deliberate sampling. the main basis of such kind of sample selection is that in it researcher by
getting pre-acquainted with the aspects of the units of universe elaborately selects the samples. Basis
of selection is the purpose of study and keeping the purpose in front, according to it researcher selects
the most representative units from the complete area. in such selection, considering the purposes as
their guide, because of doing a thoughtful selection for achieving the objective, it is called purposive
sampling. Adolph Jenson has written, “by purposive sampling it is meant that select a number of
units of universe in such a way that selected group collectively provide the same average or ratios
related to those attributes which are there in the universe and whose statistical knowledge is there
beforehand only.”
Characteristics of Purposive Sampling
1. researcher is acquainted with the attributes of all the units of the universe so that he knows
beforehand that which unit has which attribute and on that basis, by selection of which units,
purposes of study can be easily achieved.
2. In purposive sampling, selection of sampling is done by keeping any specific objective in
front. All objectives cannot be achieved through purposive sampling. still achievement of
so far as possible objectives is the target of such selection.
3. in this method, since the researcher selects the sample as per his desire, that is why there is
more possibility of bias.
Merits of Purposive Sampling—we can mention the below mentioned merits of purposive
sampling
(a) it is less expensive because in it size of samples is not very big. its belief is that if samples are
selected without bias then comparatively small sample can be representative.
(b) it is very useful in those researches in which some units of universe are especially important
and that is why their selection is required. This requirement cannot be fulfilled through
random sampling. for e.g. if educational institutions of rohelkand district have to be studied,
then inclusion of Bareily college in sample is necessary. But if we are adopting random
sampling method, then in selection of sample Bareily college may be named or may not be
named. in such situation, purposive sampling method will only be useful.

3. Stratified Sampling

hsin pao yang has written, “meaning of stratified sampling is taking sub-samples from the universe
who have common attributes like types of farming, size of farms, ownership of land, education-level,
income, gender, social class etc. such samples coming under sub-samples are taken collectively and
stratified in form of type or class.” In a more clear way, we can understand stratified sampling in
this manner- for selecting such kind of sample; researcher firstly obtains the elementary knowledge
about all attributes of the universe. on the basis of this knowledge, he divides that universe in some
classes or sub-samples so that each class represents only one attribute (like education level, income,

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