Lecture 2A: Sampling Techniques Flashcards
What is the target population?
The group of people you want to generalize your results to.
What criteria are used to define the target population?
Inclusion criteria and exclusion criteria.
What is an accessible population?
The accessible group of people that you will select your sample from.
(Sampling Frame: List of people to draw samples from)
What is a study sample?
The subgroup of people from the sampling frame who will be subjects in the study.
(Representative, have similar characteristics)
What is probability sampling?
Sampling through random selection where each member has an equal chance of being chosen.
(Unbiased, operation of chance)
What is simple random sampling?
Probability Sampling
All members are listed and selected randomly.
- E.g. Draw names from a box, Random selection by computer programs
- Least sampling bias
- But time-consuming
What is systematic sampling?
Probability Sampling
Dividing the population by the number of subjects to be selected and picking every nth name.
- Convenient and least time consuming.
- Potential bias (recurring pattern or order)
What is the sampling interval in systematic sampling?
The total number of elements in the accessible population divided by the number of elements to be selected.
What is stratified sampling?
Probability Sampling
Dividing the sampling frame into subgroups based on a characteristic relevant to the study.
- Ensures representativeness on important characteristics.
- Must have knowledge of characteristics and proportions
What is cluster sampling?
Probability Sampling
Identifying population clusters and sampling from them.
* Convenient
* Potential bias
What is non-probability sampling?
Sampling based on non-random selection where each element does not have an equal chance of being chosen.
What is convenience sampling?
Non-Probability Sampling
* Chosen on the basis of availability
* Potential bias
* Not representative of entire population
What is quota sampling?
Non-Probability Sampling
* Similar to stratified sampling
* Uses a convenience sample to get subjects for each subgroup
What is purposive sampling?
Non-Probability Sampling
Investigator hand picks subjects based on specific criteria.
What is snowball sampling?
Non-Probability Sampling
Starts with available subjects who are asked to locate others meeting the criteria.
What questions should be asked when designing a study?
- Who will be included/excluded?
- Where will I get my subjects from?
- What sampling techniques will be used?
- How many subjects do I need?
