Research methods - Sampling

    Cards (17)

    • Groups of ppts that form the research process are selected through what process?
      Sampling
    • Define population
      Group of people who the researcher is interested in studying
    • What is the researcher’s population often called?
      Target population - a subset of the general population
    • Define sample
      A group of people who take part in an investigation - drawn from the target population and presumed to be representative
    • Why should the sample drawn from the target population be representative?
      To be able to generalise findings
    • How are samples selected?
      Via sampling techniques
    • What are the 5 types of sampling techniques?
      • Random sample
      • Systematic sample
      • Stratified sample
      • Opportunity sample
      • Volunteer sample
    • What is a random sample?
      • All members of target population have equal chance of being selected
      • Need to obtain complete list of all members of TP - then all names are assigned a number
      • Sample selected through lottery method to ensure it is random
    • What is a systematic sample?
      • When every Nth member of the TP is selected e.g. every 5th pupil on a school register
      • Sampling frame is produced - a list of people in TP organised into an order e.g. alphabetical
      • Sampling system is nominated (e.g. every 5th)
      • Can begin from a randomly determined start to reduce bias
      • Researcher works through sampling frame until sample is selected
    • What is a stratified sample?
      • The composition of sample reflects the proportions of certain subgroups within the TP via strata
      • Researcher identifies the different strata that make up the population
      • Work out proportions needed for sample to be representative
      • Ppts that make up each stratum are selected using random sampling
    • What is an opportunity sample?
      • Researchers select anyone who is willing & available
      • Takes chance to ask whoever is around at time of study
    • What is a volunteer sample?
      • Ppts self select themselves to be part of the sample (self selection)
      • Researcher might place advert
      • Those who self select themselves would then make up the sample
    • What are the evaluation points for random sampling technique?
      • Potentially unbiased - confounding variables equally divided between the groups enhancing internal validity
      • Difficult & time consuming to conduct - list of TP may be difficult to obtain
      • Can still end up with a unrepresentative sample - never certain
    • What are the evaluation points for systematic sampling technique?
      • Objective method - little room for bias : researcher has no influence over who’s chosen once system for selection has been established
      • Method is time consuming & ppts can refuse to take part
    • What are the evaluation points for stratified sampling technique?
      • Can generalise findings as it produces a representative sample - designed to reflect the composition of the population
      • Identified strata might not always reflect the TP accurately - there isn’t complete representation
    • What are the evaluation points for opportunity sampling technique?
      • Convenient & less costly e.g. no list required
      • Suffer from 2 types of bias : sample is unrepresentative as it’s drawn from specific area (can’t be generalised to TP) & researcher has complete control over selection of ppts (researcher bias)
    • What are the evaluation points for volunteer sampling technique?
      • Convenient & less time consuming - requires minimal input from researcher
      • Volunteer bias - those who volunteer may have a certain ‘profile’ e.g. curious/pleasing. This can then affect how far the findings can be generalised
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