Sampling
A sample is a subset of a
larger population of objects
individuals, households,
businesses, organizations
and so forth.
Sampling enables researchers
to make estimates of some
unknown characteristics of
the population in question
A finite group is called population
whereas a non-finite (infinite)
group is called universe
A census is a investigation of all
the individual elements of a
population
The Sampling Process
1.Define the Target
population
2.Select a
Sampling Frame
3.Determine if a probability
or non-probability sampling
method will be chosen
4.Plan procedure for
selecting sampling units
5.Determine sample size
6. Select actual sampling units
7.Conduct fieldwork
Sampling Errors
Random Sampling Error – This is defined as the “difference between the sample result and the result of a census conducted using identical procedures” and is the result of chance variation in the selection of sampling units
If samples are selected properly (for e.g. through the technique of randomization), the sample is usually deemed to be a good approximation of the population and thus capable of delivering an accurate result
Usually, the random sampling error arising from statistical fluctuation is small, but sometimes the margin of error can be significant
Systematic (Non-Sampling) Errors – These errors result from factors such as an improper research design that causes response error or from errors committed in the execution of the research, errors in recording responses and non-responses from individuals who were not contacted or who refused to participate
Both Random sampling errors and systematic (non-sampling) errors reduce the representativeness of a sample and consequently the value of the information which is derived by business researchers from it
Probability Sampling – Every element in the population under study has a non-zero probability of selection to a sample, and every member of the population has an equal probability of being selected
Non-Probability Sampling – An arbitrary means of selecting sampling units based on subjective considerations, such as personal judgment or convenience. It is less preferred to probability sampling
Convenience Sampling – This is a sampling technique which selects those sampling units most conveniently available at a certain point in, or over a period, of time
Major advantages of convenience sampling is that is quick, convenient and economical; a major disadvantage is that the sample may not be representative
