Sampling
What is sampling? 1
Sampling - the selection of a fraction (subset) of the total amount of units of interest for the purposes of being able to draw general conclusions about the entire population
Data quality and sampling method are more important than sample size.
Sampling terminology? 2
Census: An investigation of ALL the individual elements that make up a population.
Population: Any complete group of entities that share some common set of characteristics.
Population element: An individual member of a population.
Sample: A subset, or some part, of a larger population.
Why sample? 3
More beneficial than census because:
Budget and time constraints.
Can still produce relatively accurate and reliable results.
Destruction of test results.
Imagine if ALL matches have to be tested for quality checks ...
What about sampling for qualitative studies (saturation point)? 4
In some qualitative research projects the research is allowed to unfold, and so the population or the samples used are sometimes not defined from the outset.
When does the researcher stop engaging participants in the research?
The answer is when the researcher reaches saturation point.
Saturation point is reached when the researcher, though continuing to explore the
phenomenon with participants in the research, no longer hears any new thoughts, feelings, attitudes, emotions, intentions, etc.
What is fieldwork? 5
Fieldwork: research work that is conducted in the field.
The work involves data gathering, and the field is any setting beyond the desk, the library and/or the laboratory in which the required data can be gathered.
e.g. Administering a questionnaire door to door, conducting telephone interviews from a central location, etc.
Sample Selection Process
What is the sample selection process? 6
Sample selection process (1 & 2) 7 1. Defining the target population
It is vital to carefully [operationally define] the target population so that the ideal data collection sources can be identified.
2. Select a sampling frame What is the sampling frame?
A list of elements (e.g. a membership list, a student email list) from which a sample may be drawn.
What is a sampling unit?
A single element or group of elements subject to selection in the sample.
Does not always have to be a person, e.g. phone numbers.
Sampling units may be categorised into:
Primary sampling units (PSU): unit selected in the 1st stage of sampling.
Secondary sampling units (SSU): unit selected in the 2nd stage of sampling.
Tertiary sampling units (TSU): unit selected in the 3rd stage of sampling.
