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Sampling (Reasons (usually not feasible to study the entire population,…

- - - - larger is usually more representative
    - - small numbers providing more in-depth information
- - - - the list of the accessible population from which you will draw a sample
  - - - Simple Random Sample
        
        each member of the population has an equal and independent chance of selection
        
        choice of one person does not bias another
        
        NOT the same as random assignment (randomization) which divides the sample into groups
      - Systematic Sampling
        
        choose every kth name on the list
        
        sometimes easier than simple random sampling
        
        generally produces a random sample, unless subjects are listed in an order that could affect outcomes
      - Stratified Sampling
        
        used if people in the population differ systematically along some characteristic and this characteristic relates to the factors being studied
        
        sampling frame is divided into subgroups or stata then samples are drawn randomly from each subgroup
        
        Proportional Stratified Sampling
        
        characteristics of interest are identified
        
        the individuals in the population are listed separately according to their classification
        
        the proportional representation of each strata
        
        a random sample is selected that reflects the proportions in the population
        
        Disproportional Stratified Sampling
        
        higher proportions are selected from some groups than others
      - Cluster Sampling
        
        used if clusters/natural groupings exist in the population
        
        instead of randomly selecting individuals units of individuals are identified and a random sample of units is then selected
    - - Convenience
        
        captive or easily sampled population
        
        bias due to self-selection
      - Purposive
        
        sample selected by the researcher based on specific (subjective) criteria
        
        more often used in qualitative research
      - Quota
        
        stratified sampling is desired, but not possible
        
        participants with the characteristic of interest are non-randomly selected until a set quota is met
      - Snowball
        
        existing subjects recruit future subjects
        
        useful in rare or hard to reach groups
        
        biased social networks