1. By :
Dr. Surendra Pal
Associate Professor
D.A.V. (P.G.) College
Muzaffarnagar, U.P.
2. Population : Aggregate of all people or items
with same characteristics.
Sample : The smaller unit of population that
is representation of population.
Probability: Chance of occurrence of an item.
Randomization: is a method of sampling in
which each item has equal chance or
probability of selection in sample.
3. True Representative
Free from Bias
Objective
Accurate
Comprehensive
Economical
Approachable
Good Size
Feasible
Practical
4. 1. Probability Sampling Techniques :
Every item chosen has a known probability to
be selected in sample.
2. Non-Probability sampling Techniques :
The items are chosen in absence of any
probability method. (or Probability of being
chosen is unknown)
5.
6. Each element of population has an equal and
independent chance of being included in
sample.
Examples:
1. Tossing a coin
2. Throwing a dice
3. Lottery method
4. Blind folded method
5. By using random table
7. Strengths Weaknesses
Essay to calculate
Minimum Knowledge of
population
Free from personal Error
Observations can be
used for inferential
purposes
Accuracy depends on
size of sample.
Applicable to small and
homogeneous samples.
Minor subgroups of
interest may not be
present in the sample.
8. Arranging the target population according to some
ordering scheme and than selecting elements and
regular intervals.
Involves a random start and then proceeds with the
selection of every kth element from then onwards. (
select each N/n th element, where N=population size
&n= sample size)
Example:
Select every 10th name from telephone directory.
9. Strengths Weaknesses
Improvement over
Simple random sampling.
Simple method
Reduce the field cost
Sample is
comprehensive &
representative
Observation is used for
conclusion and
There are different ways
of systematic list by
different peoples.
Knowledge of
population is essential.
Risk in drawing
conclusion.
It cannot ensure
representativeness.
10. Where the population is having number of distinct
categories i.e. separate strata then from each of this
homogeneous groups sample is constituted.
Using same sampling fraction for all strata ensures
proportionate representation in the sample.
11. Strengths Weaknesses
Good representation of
population.
It is improvement over
the earlier.
Objective method of
sampling.
Observation can be used
for inferential purposes
Adequate representation
of minority subgroups is
ensured.
difficult to decide
relevant criterion fro
stratification.
it is costly and time
consuming.
Require large sample
size as compare to other
method.
Sample is
representative with used
criterion and not with
other.
Complicating the
12. It is an example of 'two-stage sampling’, In first stage
a sample of areas is chosen & in Second stage a
sample of respondents within those areas is
selected.
Population divided into clusters of homogeneous
units, usually based on geographical contiguity.
Sampling units are groups rather than individuals.
A sample of such clusters is then selected.
All units from the selected clusters are studied
13. Strengths Weaknesses
Good representation of
Sampling
Easy and Economical
Method
Highly applicable in
education
Observation can be used
for inferential purpose.
It is not free from errors
It is not comprehensive.
14. Complex form of cluster sampling in which two or
more levels of units are embedded one in the other.
First stage, random number of districts chosen in all
states.
Followed by random number of talukas, villages.
Then third stage units will be houses.
All ultimate units (houses, for instance) selected at
last step are surveyed.
15. Strengths Weaknesses
Good representation of
Population.
It is improvement over
earlier methods.
An objective method of
sampling.
Observation may be
used for inferential
purpose.
It is difficult and
complex.
It involves errors while
considering primary and
secondary stages.
16. In this Samples are taken that are readily
available and convenient.
These are mostly used in pilot studies.
Example:
Interviewing person coming at Mall in given
time interval.
17. Strengths Weaknesses
Easy method of
Sampling.
Frequently used in
behavioural Science.
Economical method
as regards to time,
money and energy.
Not representative of
population.
Not free from errors.
in it parametric
statistics cannot be
used.
18. The researcher chooses the sample based on who
they think would be appropriate for the study. This is
used primarily when there is a limited number of
people that have expertise in the area being
researched.
19. Strengths Weaknesses
Knowledge of the
investigator can be best
used.
It is Economical.
It is Objective.
Not free from error.
It include uncontrolled
variation.
Inferential Statistics
cannot be used for
observations. Therefore
generalization is not
possible.
20. It combines both judgement Sampling and
probability sampling.
Selecting participant in numbers
proportionate to their numbers in the larger
population, no randomization.
Select people non randomly according to
some quota
Example:
For example you include exactly 50 males
and 50 females in a sample of 100.
21. Strengths Weaknesses
improvement over
judgement sampling.
easy sampling
technique.
most frequently used in
social surveys.
Not a representative
sample.
Not free from error.
It has influence of
regional geographical and
social factors.
22. Selecting participants by finding one or
two participants and then asking them to
refer you to others. One person
recommends another, who recommends
another, who recommends another, etc
Example:
Good way to identify hard-to-reach
populations, for example, homeless
persons, Cancer patient etc.
23. Strengths Weaknesses
Easy sampling technique.
Most frequently used where
population size is small.
Not a representative sample.
not free from error.