2. Sampling
⚫Measuring a small portion of something and then making
a general statement about the whole thing.
⚫Process of selecting a number of units for a study in such
a way that the units represent the larger group from which
they are selected.
3. Why We Need Sampling?
⚫ Sampling makes possible the study of a large, (different
characteristics) population.
⚫ Sampling is for economy
⚫ Sampling is for speed.
of data from being all
⚫ Sampling is for accuracy.
⚫ Sampling saves the sources
consumed.
4. General Types of Sampling
1. Probabilitysampling
2. Non-probabilitysampling
5. Non-probability sampling
⚫ Unequal chanceof being included in the sample (non-random)
⚫ Non random or non - probability sampling refers to the sampling process
in which, the samples are selected for a specific purpose with a pre-
determined basis of selection.
⚫ The sample is not a proportion of the population and there is no system in
selecting the sample. The selection depends upon the situation.
⚫ No assurance is given that each item has a chance of being included as a sample
⚫ There is an assumption that there is an even distribution of characteristics within
the population, believing that any sample would be representative.
7. 1. Judgment or purposive or deliberate
sampling
⚫In this method, the sample selection is purely based on the
judgment of the investigator or the researcher. This is
because, the researcher may lack information regarding the
population from which he has to collect the sample.
Population characteristics or qualities may not be known,
but sample has to be selected.
⚫In this method of sampling the choice of sample items
depends primarily on the judgment of the researcher. In
other words, the researcher determines and includes those
items in the sample which he thinks are most typical of the
universe with regard to the characteristics of research
project.
8. ⚫For example, suppose 100 boys are to be selected from a
collegewith 1000 boys. If nothing is known about the
students in this college, then the investigator may visit
thecollegeand choose the first 100 boys he meets. Or
he may select 100 boys all belonging to III Year. Or he
might select 25 boys from Commerce course, 25 from
Science courses, 25 boys from Artscoursesand 25 from
Fine arts courses. Hence, when only the sample
size is known, the investigator uses his discretion and
select the sample.
9. The useof judgmentsampling is justified by following premises:
⚫ If therearea small numberof sampling units is in the universe,
judgmentsampling enables inclusionof importantunits.
⚫ Judgmentstratificationof population helps in obtaining a more
representative sample in case research study wants to look into
unknown traitsof the population.
⚫ Judgmentsampling is a practical method toarriveatsome solution to
everyday businessproblems.
Limitations:
⚫ The judgment sampling involves the risk that the researcher may
establish conclusions by including those items in thesample which
conform to his preconceived ideas.
⚫ There is noobjectivewayof evaluating the reliabilityof sample results.
10. 2. Convenience sampling
⚫ Conveniencesampling is commonly known as unsystematic, accidental
or opportunistic sampling. According to this procedure a sample is
selected according totheconvenienceof the investigator.
⚫ In this method of sampling the choice of sample items depends
primarily on the judgment of the researcher. In other words, the
researcherdeterminesand includes those items in thesample which he
thinks are most typical of the universe with regard to the
characteristicsof research project.
⚫ A typeof non probabilitysampling which involves thesample being
drawn from thatpartof the populationwhich is close to hand. That is,
readilyavailableand convenient.
⚫ Forexample, suppose 100 carownersare to be selected. Then we may
collect from the RTO's office the listof carownersand then make a
selection of 100 from that to form the sample.
11. A conveniencesampling may be used in the following
cases:
⚫i) When universe is notwell defined,
⚫ii) When sampling unit is notclear, and
⚫iii) When complete listof the source is notavailable.
12.
13. 3. QUOTA SAMPLING
⚫ In this method, thesample size is determined first and then quota is
fixed for various categories of population, which is followed while
selecting thesample.
⚫ In this method the quota has to be determined in advance and
intimated to the investigator. The quota for each segment of the
population may be fixed at random orwitha specific basis. Normally
such a sampling method does not ensure representativeness of the
population.
⚫ Example: - Suppose we want to select 100 students, then we might say
that thesample should beaccording to thequotagiven below : Boys
50%, Girls 50% Then among the boys, 20% collegestudents, 40% plus
two students, 30% high school students and 10% elementary school
students. A differentorthe samequota may be fixed forthegirls.
14. MERITS OF QUOTA SAMPLING
⚫ Reduces cost of preparing sampleand field work, since ultimate
unitscan beselected so that theyareclose together.
⚫ Introduces somestratificationeffect.
DEMERITS OF QUOTA SAMPLING
⚫ Introduces bias of investigatoris not involved atanystage, the
errors of the method cannot be estimated by statistical
procedures.
⚫ Since random sampling is not involved at any stage, the errors of
the method cannot beestimated by statistical procedures. Quota
sampling is most commonly used in marketing survey and
election polls.
15. 4. SNOWBALL SAMPLING
⚫Itrefers to Identifying someonewho meets thecriteria
for inclusion in the study.
⚫Selection of additional respondents is based on
referrals from the initial respondents.
