Sampling Flashcards
What are the 5 types of sampling?
Random
Systematic
Stratified
Opportunity
Volunteer
What is sampling?
Selecting participants from a target population to take part in an experiment.
What is a target population?
The subgroup of people with a particular characteristic the researcher intends to study.
The findings from the representative sample will be generalised.
What is random sampling?
Every member of the ENTIRE target population has an EQUAL chance of being selected.
E.G. pulling names from a hat OR using a computer generator that randomly selects without bias.
What are the strengths of random sampling?
= No researcher bias =
Bc sample is selected randomly - researcher has no say as to who’s selected - sample is representative and can be generalised to TP.
What are the weaknesses of random sampling?
= Time consuming & Unwillingness =
Difficult and time-consuming to ensure everyone in TP has an equal chance of being selected. Participants may not be willing to take part.
What is systematic sampling?
Predetermined system used to select pps.
Every nth person from a LIST of the TP is selected from a register, phonebook…etc.
E.G. (every 10th, 15th, 25th person from a list)
What are the strengths of systematic sampling?
= Less researcher bias =
Participants selected by a predetermined system instead of researcher selecting pps by choice - have no say - sample representative of TP.
What are the weaknesses of systematic sampling?
= Sample may slightly be biased =
Not truly unbiased - may be possible that every nth person have a particular characteristic in common, (E.G. being right-handed) - sample may not be representative - difficult to generalise.
What is a stratified sample?
Participants are selected from each category in subgroups in proportion to their occurrence within the population.
E.G. if a class of A-Level psychology has 20 students: 18 males & 2 females, and researcher wanted a sample of 10 to participate in study, the sample would consist of 9 males and 1 female, to represent population proportionally.
What are the strengths of stratified sampling?
= Less researcher bias =
Sample generated randomly once subgroups have been identified - reduces chance that researcher chooses a biased sample of pps who would support their aims - more representative sample - can be generalised - high population validity.
What are the weaknesses of stratified sampling?
= Difficult & Time-consuming =
Difficult and time-consuming - ensuring subgroups in TP are identified.
Pps selected may be unwilling to take part.
What is opportunity sampling?
Selecting anyone who is AVAILABLE and WILLING to take part in study at the time.
What are the strengths of opportunity sampling?
= Quicker and easier to obtain =
Bc it requires less effort - ask anyone from TP in the area to take part - saves money - cheap.
What are the weaknesses of opportunity sampling?
= Bias issues =
Sample drawn from a specific area/location (E.G. university) - likely students/pps not representative of TP.
= Investigator bias =
Bc researcher has complete control over who they approach - may select particular pps or avoid others because of their own subjective preference.
