Sampling

• What is the acronym for the different types of sampling?

  VROSS
• VROSS


  Volunteer, Random, Opportunity, Systematic, Stratified
• Random sampling


  Every person has an equal chance of being picked for the experiement. It requires a whole list of the target population, which can be time-consuming.
• Stratified sampling


  The strata sample has the same proportion as the target population.
• Opportunity sampling is where a researcher approaches members of the public who are willing to be participants of the study.
• Systematic sampling


  Researcher selects every nth person from the target population.
• Random Sampling 


  Researcher gathers a list of the entire population, and picks participants, at random, without bias. This can be done with a 'spin-the-wheel' or with names in a hat.
• Stratified Sampling 


  Researchers sample so that their sample has the same proportion of each sub-group of the total population. To do this, researchers first identify important sub-groups within the population. Second, they identify how many people are needed for the sub-group to have the same proportion as the original population. Finally, researchers sample randomly from each subgroup until they get that number.
• Both volunteer and opportunity sampling are quick and easy, but the sample will not be as representative of the target population. This is because volunteer sampling attracts people interested in what is being studied, whereas Opportunity attracts people who would want to do the research on the same day.
• Volunteer sampling is easier than opportunity, making it more cost-effective whereas opportunity sampling is more representative than volunteer sampling, making it a more valid way of sampling.
• A strength of stratified sampling is that it ensures that the sample represents the whole population. However, it requires a lot of effort to work out the proportions of different sub-groups in the population. It also takes a long time to collect data from such a diverse range of people.
• A strength of systematic sampling is that it ensures all groups are represented equally. A weakness is that if there are too few people in one group then it may take longer to find enough participants. It also means that some people might be missed out altogether.
• Systematic sampling is more likely to lead to a more representative sample that volunteer or opportunity sampling. This is because it involves sampling from the entire population, however systematic sampling is more difficult than both sampling techniques due to requiring an entire list of the population, which can be time-consuming.

  Another limitation is that if there is a pattern in the data listed, the sample may not be representative.
• A strength of Random sampling is that it is representative - every member of the population has an equal chance of being included.

  • So it is more representative that volunteer, opportunity & systematic

  However, it is difficult, as you will need an entire list of the target population, and a way to randomise, making it more time-consuming than the named sampling techniques.

  Random Sampling also does not guarantee that the sample will look like the population - not fully representative
• Stratified sampling is the most representative than all other types of sampling. The sample would most likely look like the target population so results should generalise to the target population, and have high population validity.

  • Researchers may miss out an important subgroup - which means the sample may not be completely representative
  • There are many steps to stratified sampling, making more time-consuming and economical which is not cost-effective.
• There are five different sampling techniques/methods.

  A) representative

  B) representative

  C) volunteer

  D) opportunity

  E) systematic

  F) Random

  G) Stratified

  H) Easier

  I) Harder