Sampling Flashcards
Random Sample
A sophisticated form of sampling in which all members of the target population have an equal chance of being selected
How to do a random sample?
- Obtain a complete list of all members of the target population
- Assign each name a number
- Sample is generated through the use of a lottery method
‘Lottery methods’
- Pick numbers out of a hat
- Computer based randomiser (only use if completely necessary; best to use a manual method)
Random Sampling
Strengths
- Free from researcher bias; no influence over who is selected
Random Sampling
Limitations
- Difficult, time consuming to conduct
- A complete list of the TP may be hard to obtain
- Sample may still be unrepresentative
- Selected PPs may refuse to take part
Systematic Sample
When every nth number of the TP is selected
How to do a systematic sample?
- A sampling frame is produced
- A sampling system is nominated/determined randomly to reduce bias
- Researcher works through sampling frame until complete
‘Sampling frame’
A list of people in the TP organised - eg. into alphabetical order
Systematic Sampling
Strengths
- Avoids researcher bias
- Fairly representative
Systematic Sampling
Limitations
- There is still the probability of getting an unrepresentative sample (unlikely)
Stratified Sample
The composition of the sample reflects the proportion of people in certain strata within the TP or wider population
‘Strata’
Sub-groups
How to do a stratified sample?
- Researcher first identifies the different strata that make up the population
- Proportions needed for the sample to be representative are worked out
- The participants that make up each stratum are selected using random sampling
Stratified Sampling
Strengths
- Avoids researcher bias: once the TP has been subdivided into strata, the PPs are randomly selected
- Representative sample as it is designed to accurately reflect the composition of the population
- Generalisation of findings becomes possible
Stratified Sampling
Limitations
- Not perfect; the strata can’t reflect all the ways that people are different. Complete representation of the TP is impossible
Opportunity Sample
A sample where researchers select anyone who happens to be willing and available
How to do an opportunity sample?
- Researcher simply takes the chance to ask whoever is around at the time of their study
Opportunity Sampling
Strengths
- Convenient; less time and effort
- Less costly
Opportunity Sampling
Limitations
- Unrepresentative of TP as it is drawn from a very specific area
- Researcher bias
Volunteer Sample
Participants select themselves to be part of the sample, hence aka ‘self-selection’
How to do a volunteer sample?
- Researcher may place an advert or willing PPs may volunteer when researcher asks
Volunteer Sampling
Strengths
- Easy; minimal input is required from researcher
- Less time-consuming
Volunteer Sampling
Limitations
- Volunteer bias
- May attract a certain ‘profile’ of a person (helpful, keen, curious)
- Can affect how far findings can be generalised
