Sampling

    Cards (19)

    • Population
      A group of people who are the focus of the researcher's interest, from which a smaller sample is drawn.
    • Sample
      A group of people who take part in a research investigation. The sample is drawn from a target population and is presumed to be representative of that population, i.e. it stands 'fairly' for the population being studied.
    • Sampling techniques
      The method used to select people from the population.
    • Bias (in the context of sampling)
      When certain groups are over or under represented within the sample selected. This limits the extent to which generalisations can be made to the target population.
    • Generalisation
      The extent to which findings and conclusions from a particular investigation can be broadly applied to the population. This is possible if the sample of pps is representative of the target population.
    • Systematic sample
      When every nth member of the target population is selected. A sampling frame is produced, which is a list of people in the target population organised in a certain way. A sampling system is nominated. May begin from a randomly determined start to reduce bias. Researcher works through sampling frame until sample is complete.
    • Stratified sample
      Sophisticated form of sampling in which the composition of the sample reflects the proportions of people in certain subgroups within target/wider population. Researcher first identifies different strata that make up population. Proportions needed for sample to be representative are worked out. Finally, participants that make up each stratum are selected using random sampling.
    • Opportunity sample
      Selecting anyone who happens to be willing and available. The researcher simply takes the chance to ask whoever is around at the time of their study.
    • Volunteer sample
      Involves participants selecting themselves to be part of the sample; also referred to as self-selection. To select a volunteer sample, a researcher may place an advert in a newspaper or on a common room noticeboard. Alternatively, pps may simply raise their hand when the researcher asks.
    • Weaknesses of random sample
      • Obtaining a complete list of the target population may be extremely difficult
      • Still may end up with a sample that is unrepresentative
      • Selected participants may refuse to take part
    • Strengths of random sample
      • Sample is potentially unbiased; CVs and EVs should be equally divided between different groups - enhances internal validity
    • Weaknesses of systematic sample
      • Time consuming
      • Pps may refuse to take part
    • Strengths of systematic sample
      • Method is objective; once system for selection has been established the researcher has no influence over who is chosen
    • Weaknesses of stratified sample
      • Identified strata cannot reflect all the ways that people are different, so complete representation of the target population is not possible
    • Strengths of stratified sample
      • Produces a representative sample because it is designed to accurately reflect the composition of the population - generalisation of finding is possible
    • Weaknesses of opportunity sample
      • Sample is unrepresentative of target population as it is drawn from a specific area, so findings cannot be generalised to target population
      • Researcher has complete control over selection of participants and may avoid people they do not like the look of - researcher bias
    • Strengths of opportunity sample
      • Much less costly in terms of time and money + no need to divide the population into different strata - convenient
    • Weaknesses of volunteer sample
      • Asking for volunteers may attract a certain 'profile' of person; one who is curious and more likely to try and please the researcher - might affect how far findings can be generalised
    • Strengths of volunteer sample
      • Requires minimal input from the researcher - easy and less time-consuming
      • Researcher end sup with pps who are more engaged
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