sampling

• population- the large group of people that are research is interested in studying
• sample- usually not possible to include all members of the population in the study, so smaller group is selected (sample)
• Random sampling is when every person in the target population has an equal chance of being selected. Select people by random name generator or pulling names out of a hat
• Strength and limitation of random sampling:

  • Potentially unbiased – this means extraneous and confounding variables are controlled. This enhances internal validity
  • Time-consuming and may not work – the complete list of population is hard to get. Also some participants may refuse to take part
• Systematic sampling is participants are selected using a set of pattern like list in alphabetical order and every nth person is selected from a list of the target population
• Strength and limitation of systematic sample:

  • Unbiased – the first item is usually select at random. This is an objective method
  • Time and effort – a complete list of the population is required. May as well use random sampling
• Stratified sampling reflects proportions of people in certain subgroups within a population. Subgroups identified like gender of age and the relative percentages of the sub groups in the population are reflected in the sample
• Strength and limitation of stratified sampling:

  • Representative method – the characteristics of the target population are represented. Generalisability more likely than other methods
  • Stratification is not perfect – subgroups cannot reflect all the ways in which people are different. Complete representation is not possible
• Opportunity sampling is when people who are simply most available are selected for the study like asking people nearby
• Strength and limitation of opportunity sampling:

  • Quick method – convenient because you make use of the people who are closest. This makes it cheaper and one of the most popular something methods
  • Biased – samples is unrepresentative of the target population at is it drawn from a very specific area such as one street in 1 town. This means that the findings cannot be generalised
• Volunteer sampling is when participants select themselves when they see an advert in a newspaper or asked to put their hands up
• Strength and limitation of volunteer sampling:

  • participants are willing – participants know how much time and effort is involved and are likely to engage more than people stopped in the street
  • Volunteer bias – participants may share certain traits like wanting to be helpful. This means generalisation is limited