sampling

• What is a target population?

  A large group of people in society, researchers want to generalise findings to the population.
• What is a sample?

  A small group of people picked to take part in research, researchers want to generalise findings from this group to the population.
• Name 5 sampling methods.

  Random

  Opportunity

  Systematic

  Stratified

  Volunteer
• What is random sampling?

  This method gives every member of the target group an equal chance of being selected for the sample
• How is random sampling done?

  By assigning a number to each member, and then selecting from the pool at using a random number generator
• What is a strength of random sampling?

  There is a reasonable chance of achieving a representative sample, making the results easier to generalise to the population
• What is a weakness of random sampling?

  It can be impractical (or not possible) to use this technique, e.g. the target group may be too large to assign numbers to.
• What is opportunity sampling?

  It is the simplest form of sampling and involves selecting anyone who is available from the target population and willing to take part.
• What is a strength of opportunity sampling?

  This method is easy and inexpensive to carry out, for this reason it is a popular sampling method
• What is a weakness of opportunity sampling?

  The consequent sample may not be representative as it could be subject to bias, making the results harder to generalise to the population
• How might an opportunity sample be subject to bias?

  The conveniently located researcher may undertake a selection process in a place where only a limited type of person is available
• What is systematic sampling?


  A systematic method is chosen for selecting from a target group
• How is systematic sampling different to random sampling?

  It does not give an equal chance of selection to each individual in the target group
• How is systematic sampling done?

  A sampling frame is chosen, for example, alphabetical order. Every nth person is chosen
• What is a strength of systematic sampling?

  Assuming the list order has been randomised, this method offers an unbiased chance of gaining a representative sample, making the results easier to generalise to the population
• What is a weakness of systematic sampling?

  It can be impractical (or not possible) to use this technique, e.g. the target group may be too large to assign numbers to.
• What is stratified sampling?

  The target population is divided into sub-sets e.g. age, gender, class etc. and a random sample is taken from these sub-sets. This ensures that the sample is representative of the population.
• Provide an example of stratified sampling.

  If a target population consisted of 75% women and 25% men, a sample of 20 would include 15 women and 5 men.
• What is a strength of stratified sampling?

  The sample is guaranteed to be representative, making the results generalisable to the population
• What is a weakness of stratified sampling?

  It is a lot of time and resources to plan and execute, for this reason it usually isn't chosen by researchers
• What is volunteer sampling?

  Participants sign up to take part in the experiment
• How is volunteer sampling done?

  For example from a newspaper advert or email
• What is a strength of volunteer sampling?

  This often achieves a large sample size through reaching a wide audience relatively easily, for this reason it is the most popular sampling method
• What is a weakness of volunteer sampling?

  Those who respond to the call for volunteers may all display similar characteristics thus increasing the chances of yielding an unrepresentative sample, making the results harder to generalise to the population
• How might a volunteer sample display similar characteristics?

  Such as being more trusting or cooperative than those who did not apply