TYPES OF SAMPLING

• What is sampling?

  The difference between population and sample; sampling techniques include random, systematic, stratified, opportunity and volunteer.
• What is population?

  An entire group with specific characteristics.
• What is time sampling?

  A research method that involves observing and recording behaviour at specific time intervals.
• What is event sampling?

  This involves observing the whole event from start to finish, tallying the behaviours when they arise.
• What is random sampling?


  A method of selecting a subset of individuals from a larger population in a way that each individual has an equal chance of being chosen.
• What is a strength of random sampling?

  It is widely accepted that since each member has the same probability of being selected, there is a reasonable chance of achieving a representative sample.

  less bias

  less demand characteristics.
• What are 2 weaknesses of random sampling?

  • Small minority groups within your target group may distort results, even with a random sampling technique.
  • It can be impractical (or not possible) to use a completely random technique, e.g. the target group may be too large to assign numbers to.
• What is systematic sampling?

  
  

  A systematic method is chosen for selecting from a target group, e.g. every fourth person in a list could be used in the sample. It differs from random sampling - it does not give an equal chance of selection to each individual in the target group.
• 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.
• What is a weakness of systematic sampling?

  If the list has been assembled in any other way, bias may be present. For example if every fourth person in the list was male, you would have only males in your sample.
• What is stratified sampling?

  The sampler divides the target group into sections, each showing a key characteristic which should be present in the final sample - each of those sections is sampled individually. The sample created should contain members from each key characteristic in a proportion representative of the target population.
• What is a strength of stratified sampling?


  It avoids the problem of misrepresentation sometimes caused by purely random sampling.
• What is a weakness of stratified sampling?

  It takes more time and resources to plan - otherwise bias will occur.
• What is opportunity sampling?

  Participants who are both accessible and willing to take part are targeted.
• What is a strength of opportunity sampling?

  
  

  Easy and inexpensive to carry out.
• What his a weakness of opportunity sampling?

  The consequent sample may not be representative as it could be subject to bias
• What is volunteer sampling?

  The sample consists of people who have volunteered to be in the study.
• What is a strength of volunteer sampling?

  This often achieves a large sample size through reaching a wide audience, e.g. with online advertisements.
• What is a weakness of volunteer sampling?


  Those who respond to the call for volunteers may all display similar characteristics - increases the chances of yielding an unrepresentative sample
• What is a representative sample?

  A subset of the target group with a similar distribution of relevant characteristics, which allows us to generalise from the sample to the target group with some justification.
• What is an unrepresentative sample?

  One that does not reflect the distribution of characteristics of the target group, cannot be generalised to the target population, and is therefore biased.