This document discusses population and sampling methods in research. It defines key terms like population, element, sample, and subject. It also explains different sampling techniques such as random sampling, stratified sampling, cluster sampling, and non-probability sampling methods like convenience sampling, quota sampling, and judgmental sampling. The document outlines advantages and disadvantages of each sampling method and notes that determining an appropriate sample size is important for making valid statistical inferences about a population.

1. Population and Sampling
Chapter 9:
COURSE INSTRUCTOR: Dr. AFTAB

2. Population and Element; Sample and
Subject
Population:
The entire group under study as defined by research
objectives
Element:
An element is the single member of the population
Sample:
A sample is a subset of the population that should
represent the entire group.
Subject:
A subject is the single member of the sample (Just as element
is a single member of the population)

3. Sampling is the process of selectingobservations
(a sample) to provide all information about of
the population.
Sample
It is aunit that is selected from
population
Represents the whole population
Sampling Frame
Listing of population from which asample ischosen

4. Population
Sample
Sampling
Frame
Sampling
Process
What you
want to
talk about
What you
actually
observe
in the
data

9. All subsets of the frame are given an equa
l
probability.
Random number generators

10. Population is divided into two or more groups
called strata
Subsamples are randomly selected from e
a
c
h
strata

11. Thepopulation is divided into subgroups (clusters) like
families.
Asimple random sample is taken from eachcluster

12. Order all units in the samplingframe
Then every number on the list isselected
N=Sampling Interval

14. Theprobability of each casebeing selected from t
h
e
total population is not known.
Units of the sample are chosen on the basisof
personal judgment or convenience.
There are NOstatistical techniques for measuring
random sampling error in anon-probability sample.

15. A. Convenience Sampling
B.Quota Sampling
C.Judgmental Sampling (PurposiveSampling)

16. Convenience sampling involves choosing respondents
at the convenience of theresearcher.
Advantages
Very low cost
Extensively used/understood
Disadvantages
Variability and bias cannot be measured or controlled
Projecting data beyond sample not justified
Restriction of Generalization.

17. Thepopulation is first segmented into mutually
exclusive sub-groups, just asin stratified sampling.
Advantages
Usedwhen research budget is limited
Very extensively used/understood
No need for list of populationelements
Disadvantages
Variability and bias cannot be measured/controlled
Time Consuming
Projecting data beyond sample not justified

18. Researcheremploys his or her own "expert”
judgment about.
Advantages
There is aassuranceof Quality response
Meet the specificobjective.
Disadvantages
Biasselection of sample mayoccur
Time consuming process.

19. Sample size determination is the act of
choosing the number of observations or replicates to
include in a statistical sample. The sample size is an
important feature of any empirical study in which the
goal is to make inferences about a population from a
sample. In practice, the sample size used in a study is
usually determined based on the cost, time, or
convenience of collecting the data, and the need for it
to offer sufficient statistical power.
Determination of sample size