Popluation, sample and sampling

• Population 


  The group of people who are the focus of the research and from which the sample is drawn

  -Popluations are normally described in terms of their demographics eg. age, gender, occupation
• Strata 


  Different demographic characteristics (such as age, socioeconomic status or gender)
• Sample 


  A subset of the research population who participate in a study
• Representative sample 


  To make a sample representative, it must have the same proportion of relevant demographics as the target population

  -Achieveing a representative is dependent on

  -Size (the bigger the sample, the more likely it is to be representative of the population)

  -Sampling techniques used (how a sample is selected can determine whether it is based or representative)
• Generalisability 


  When evaluating generalisability consider:

  -the appropriateness and application of data to different cultural groups

  -The external validity of the research study and whether the finding can be applied to similar individuals in a different setting

  -The implications the results may have for a group of people wider than the original sample.
• Sampling technique


  The way a sample is selected from the population for a study
• Convenience sampling 


  Any sampling technique that involves selecting readily available members of the population
• Random sampling 


  Any sampling technique that uses a procedure to ensure every member of the population has the same chance of being selected
• Stratified sampling 


  Any sampling technique that involves selecting people from the population in a way that ensures that is strata (subgroups) are proportionally represented in the sample
• To collect a stratified sample 


  -Divide the research population into different strata based on characteristics relevant to the study

  -Select participants from each stratum in proportion to how they appear in the population
• Advantage of convenience sampling

  -The most time-effective and can be cost-effective
• Limitations of convenience sampling 


  -The most likely to produce an unrepresentative sample, thereby making it harder for researchers to generalise results to the popluation
• Advantages of random sampling

  -The sampling generated can be more representative than convenience sampling

  -It reduces experimenter bias in selecting participants

  -It can make a fairly representative sample if the sample is large
• Limitations of random sampling 


  -It may be time-consuming to ensure every member of a population has an equal chance of being selected for the sample

  -It may not create an entirely representative sample when the sample is small
• Advantages of stratified sampling 


  -The most likely to produce a representative sample
• Limitations of stratified sampling 


  -It may be time-consuming and expensive

  -It can be demanding on the researcher to select the most appropriate strata to account for
• Allocation 


  The process of assigning participants to experimental conditions or groups

  -Should use random allocation: a type of allocation which ensures every sample participant has an equal chance of being allocated to any group within the study