SCS 2150 Chapter Notes - Chapter 8: Simple Random Sample, Quota Sampling, Convenience Sampling

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(6) Chapter 8: Selecting a Sample
Sampling is used in all quantitative and qualitative research unless the researcher is not
interested in drawing conclusions for a larger population or if the researcher can easily
study all members of the group about whom they wish to draw conclusions, allowing for
the whole population to be studied.
Part of the whole is studied, and the results are taken to be an accurate reflection of the
whole. Only if the sample studied can be shown to represent a larger population can the
result of a study of the sample be assumed to give reliable information about the larger
population. If the sample is not representative, the conclusions drawn from the research
must be limited to the sample studied.
Why do researchers sample? To reduce the cost in time, energy, and money of studying
large populations and because it is impossible and undesirable to study everyone.
How to Select a Sample
You must identify the population about which you want to know something and draw
reliable conclusions about, and then you must select a sampling procedure.
Types of Sampling Procedure
Non-random sampling procedures: These provide only a weak basis for generalization.
They are suited for qualitative research studies where the goal is a deeper understanding
of the phenomena or situation rather than making inferences to a larger population.
oAccidental sampling (haphazard sampling): Using what is immediately available.
The researcher does not know in what ways the sample is biased without doing a
study of everyone or a study of a properly drawn random sample which means
that the findings of the study are strictly limited to those studied. However, the
researcher can handpick participants who meet the criteria of providing the best
information about the issue of the study.
oAccidental quota sampling: Selecting individuals or groups on the basis of set
criteria. By filling your quota, you make sure that your sample includes people or
groups with certain specified characteristics to ensure that they adequately
represent the sample for you analysis. This procedure is often used because of
time and budget pressures.
oPurposive sampling (judgmental sampling): Researchers believe that they can,
using their own judgment or intuition, select the best people or groups to be
studied. It is appropriate for case study and qualitative approaches in which the
intent is not to generalize to a larger population but to examine a ‘typical’ case in
order to understand it more fully. According to Neuman and Robson (2009),
purposive sampling is appropriate: for selecting cases that are illustrative of a
phenomena; for selecting ‘difficult to reach’ members of a unique population; or
for identifying particular types for investigation in greater detail. In other words,
this procedure is appropriate for studying extreme cases of a phenomenon.
oSnowball technique: Used when you need to gain access to certain types of people
or to a particular group, but you know only a few people who fit the category and
there is no publicly available listing. You gather your sample by first approaching
those who are available and then asking them to nominate others whom they
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