1.3 Non-random sampling

• In quota sampling, an interviewer or researcher selects a sample that reflects the characteristics of the whole population.
• Opportunity sampling consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for.
• Advantages of quota sampling

  • Allows a small sample to still be representative of the population
  • No sampling frame required
  • Quick, easy and inexpensive
  • Allows for easy comparison between different groups within a population
• Disadvantages of quota sampling

  • Non random sampling can introduce bias
  • Population must be divided into groups, which can be costly or inaccurate
  • Increasing scope of study increases number of groups, which adds time and expense
  • Non responses are not recorded as such
• Advantages of opportunity sampling

  • Easy to carry out
  • Inexpensive
• Disadvantages of opportunity sampling

  • Unlikely to provide a representative sample
  • Highly dependant on individual researcher