Page 102 - DLIS401_METHODOLOGY_OF_RESEARCH_AND_STATISTICAL_TECHNIQUES

Unit 6: Sampling Techniques

Quota sampling is the nonprobability equivalent of stratified sampling. Like stratified sampling, Notes
the researcher first identifies the stratums and their proportions as they are represented in the
population. Then convenience or judgment sampling is used to select the required number of
subjects from each stratum. This differs from stratified sampling, where the stratums are filled
by random sampling.
Snowball sampling is a special nonprobability method used when the desired sample characteristic
is rare. It may be extremely difficult or cost prohibitive to locate respondents in these situations.
Snowball sampling relies on referrals from initial subjects to generate additional subjects.
While this technique can dramatically lower search costs, it comes at the expense of introducing
bias because the technique itself reduces the likelihood that the sample will represent a good
cross section from the population.

Notes Practicability of statistical sampling techniques allows the researchers to estimate
the possible number of subjects that can be included in the sample, the type of
sampling technique, the duration of the study, the number of materials, ethical
concerns, availability of the subjects/samples, the need for the study and the amount
of workforce that the study demands.

Sampling and Data Collection
Good data collection involves:
• Following the defined sampling process

• Keeping the data in time order
• Noting comments and other contextual events

• Recording non-responses
Most sampling books and papers written by non-statisticians focus only in the data collection
aspect, which is just a small though important part of the sampling process.

Self Assessment

Multiple Choice Questions:
1. ........................ is the purest form of probability sampling.
(a) Random sampling (b) Stratified sampling

(c) Systematic sampling (d) Convenience sampling.
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2. ........................ is also called an N name selection technique.
(a) Stratified sampling (b) Systematic sampling
(c) Random sampling (d) Judgment sampling.

3. ........................ is commonly used probability method that is superior to random sampling
because it reduces sampling error.
(a) Convenience sampling (b) Judgment sampling

(c) Stratified sampling (d) Random sampling.

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