sampling

• what is sampling?

  the group which is included in a study, so that the researchers don’t have to include everyone.
• volunteer sampling:


  when researcher posts an advert and participants volunterr
• strengths and weaknesses of volunteer sampling

  strengths:

  • quick and easy

  weaknesses:

  • not representative of population
• what is opportunity sampling

  when the researcher uses people in their surroundings to construct a sample
• strengths and weaknesses of opportunity sampling:

  strengths:

  • quick and easy to get participants

  weaknesses:

  • not representative of participants
• systematic sampling 


  when researchers pick the nth person from an entire population
• strengths and weaknesses of systematic sampling

  strengths:

  • likely to lead more representative sample as involves from whole population

  weaknesses:

  • difficult because the researcher has to obtain a list of the whole populations
  • if there is a pattern on how data is listed, sample may not be representative
• what is random sampling?

  Picking randomly from a list of the entire population, so that everyone has an equal chance of being a participant.
• strengths and weaknesses of random sampling

  strengths:

  • representative because every member of the population has an equal chance of being included.

  
  

  weaknesses:

  • difficult as need a list and way to generate picking at random
  •  It still doesn’t guarantee that the sample will look like the population.
• stratified sampling 


  sample so that their sample is the same proportion of each subgroup as the total population.
• how to do stratified sampling:

  1. identify important subgroup in a population that you need
  2. identify how many people from each subgroup are needed to have the same proportion as the original
  3. randomly sample from each subgroup to get that number
• strengths and weaknesses of stratified sampling:

  strengths:

  • most representative that all other sampling techniques so able to generalise to whole population (high population validity)

  weaknesses:

  • difficult and time consuming because of many steps involves
  • Researchers may miss out an important subgroup by mistake.
• most of the studies that you’ll see in psychology use…

  volunteer and opportunity