sampling techniques

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  • sampling techniques
    • random sampling
      • everyone has an equal chance of being picked
      • strengths
        • convient - researchers need committed ppt- less likely to drop out
          • good way to get specialised group of people- purposivesampling
      • weaknesses
        • likely to be biased- as volunteers motivated/ more willing than general public
          • can't generalise
          • volunteer also more helpful = prone to guessing aims
            • likely too respond to demand characteristics
    • opportunity sampling
      • whoever is willing and available
      • strengths
        • most convient-little prep
          • takes the least amt of time
          • may be only technique available
      • weaknesses
        • inevitablybiased- sample is from small group
          • not represntative - can't generalise
          • ppt may refuse to take part- final sample has same as volunteer sample
            • open to demand characeteristics
    • random sampling
      • every member of target population has equal chance of being selected
      • strengths
        • unbiased + all members have equal chance
          • possible to choose specific subgrouptaget pop- makes easy to select
      • weaknesses
        • biased  sample if not all selected want to take part
          • take time- need to obtain all names then choose then contact
            • not often random- not all want to take part- ends up like volunteer/opp sample
    • stratified sampling
      • ppt selected from diff subgroups (strata) which are proportional to target pop
      • strengths
        • most representative - all in proportion
          • specific subgroups - chosen according to variables
            • increases-control over possible extraneous variable
        • weaknesses
          • subgroup might be biased- not representative
            • lengthy process- ppt may not agree to participate


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