The document discusses four types of non-probability sampling: convenience sampling, purposive sampling, quota sampling, and snowball sampling. Convenience sampling involves readily available subjects but lacks representation of the overall population. Purposive sampling selects subjects with specific characteristics. Quota sampling aims for a predetermined percentage of certain groups. Snowball sampling starts with a few subjects who then refer additional subjects.

1. 
10/14/2022
Types of Non-Probability Sampling
Convenience Sample (Available Sample)
Purposive Sampling
Quota Sampling
Snow-Ball Sampling
Muhammad Awais
(facebook.com/awwaiis)

2. 
 It is a collection of readily accessible subjects,
elements, or events for study, such as a group of
students enrolled in an introductory mass media
course or shoppers in a mall.
 Although available samples can be helpful in
collecting exploratory information and may produce
useful data in some instances, the samples are
problematic because they contain unknown
quantities of error. Researchers need to consider the
positive and negative qualities of available samples
before using them in a research study.
10/14/2022
Convenience Sample (Available
Sample)
Muhammad Awais
(facebook.com/awwaiis)

3. 
 Critics argue that regardless of what results they generate, available
samples do not represent the population and therefore have no
external validity. The respondents are included in a study solely on
the basis of their availability.
 For example, mall intercept studies are criticized because only the
people who are at the mall at the time of the study have a chance to
participate. No one outside the mall has such an opportunity.
 The Law of Large Numbers
 If the researchers interview thousands of respondents instead of
hundreds. The presumption is that the large number of respondents
eliminates the problems of convenience sampling and somehow
compensates for the fact that the sample is not random.
10/14/2022
Muhammad Awais
(facebook.com/awwaiis)

4. 
 In most situations, available samples should be
avoided but available samples can be useful in
pretesting questionnaires or other preliminary (pilot
study).
 Available samples often help eliminate potential
problems in research procedures, testing, and
methodology before the final research study, with an
appropriately selected sample, is conducted.
10/14/2022
Muhammad Awais
(facebook.com/awwaiis)

5. 
 It includes respondents, subjects, or elements
selected for specific characteristics or qualities and
eliminates those who fail to meet these criteria.
 Not only because of the proximity to the researcher.
10/14/2022
Purposive Sample
Muhammad Awais
(facebook.com/awwaiis)

6. 
 Subjects are selected to meet a predetermined or
known percentage.
 For example, a researcher interested in finding out
how DVD owners differ from nonDVD owners in
their use of television may know that 40% of a
particular population owns a DVD. The sample the
researcher selects, therefore, would be composed of
40% DVD owners and 60% non-DVD owners (to
reflect the population characteristics).
10/14/2022
Quota Sampling
Muhammad Awais
(facebook.com/awwaiis)

7. 
 The term snowball sampling is used most often in
academic research. In private sector research, this
approach is known as referrals.)
 In either case, the method is the same. A researcher
(or research company or field service) randomly
contacts a few qualified respondents and then asks
these people for the names of friends, relatives, or
acquaintances they know who may also qualify for
the research study. These referrals are then contacted
to determine if they qualify for the research.
 The sample may be completely biased.
10/14/2022
Snow-ball Sampling
Muhammad Awais
(facebook.com/awwaiis)