Sampling

• Population


  A group of individuals that a researcher is interested in studying
• Sample


  A relatively small proportion of people who are chosen in a survey so as to be representative of the whole.
• Generalisation


  - The extent to which findings and conclusions from a particular experiment can be broadly applied to the population.

  - This is possible if the sample of people is representative of the population.
• Bias


  A particular preference or point of view that is personal, rather than scientific.
• Sampling technique


  The method used to obtain the participants for a study from the population
• Random sample


  A sample that fairly represents a population because each member has an equal chance of inclusion

  
  

  - Unbiased

  - Difficult and time-consuming.

  - Can be unrepresentative.

  - May refuse to take part.
• Systematic sample


  A sample drawn by selecting individuals systematically from a sampling frame

  
  

  - Objective

  - Time-consuming

  - Can refuse to take part
• Stratified sample


  A sample drawn in such a way that known subgroups within a population are represented in proportion to their numbers in the general population

  
  

  - Representative

  - Generalisable

  - Not completely representative
• Opportunity sample


  A sample of participants produced by selecting people who are most easily available at the time of the study.

  
  

  - Convenient

  - Less time-consuming

  - Inexpensive

  - Unrepresentative

  - Researcher bias
• Volunteer sample


  A method of sample selection that consists of people choosing themselves by responding to a general appeal.

  
  

  - Easy

  - Volunteer bias