Sampling

Sampling

1. Key terms

   • Population - Group of people who are the focus of the researchers interest...from which a smaller sample is drawn.
   • Sample - Group of people who take part in a research investigation. The sample is drawn from a target population and is presumed to be a representation of that population.
   • Sampling Techniques - Method used to select people from a population
   • Bias - When certain groups are under or over-represented within a selected sample
   • Generalisation - The extent to which findings and conclusions from a particular investigation can be applied to the population which is possible if the sample is representative of the population

2. Random Sample

   • Sophisticated form of sampling where all members of the target population have an equal chance of being selected for a sample.
   • A list of all possible participants for a sample is created, each one assigned a number and then a random number generator is used to select them
   • Free from researcher bias, therefore is widely generalisable to the rest of the population
   • Difficult and time-consuming to conduct
   • May not represent the rest of the population accurately

3. Systematic Sample

   • Every nth member of the target population is selected for the sample
     • Sampling frame is produced which is a list of people in the target population, typically organised somehow, like in alphabetical order
   • Known to be fairly representative of the target population
   • Avoids research bias - researchers have no control over sample as it's calculated using a formula/method

4. Stratified Sample

   • Form of sampling in which the composition of sampling reflects the proportions of the people in the strata within the target population
     • First, the strata within the target population is identified
       • Proportion between the strata is identified
         • Sample is completed using the selections in proportion to the ratio of sample options
   • Avoids researcher bias
     • After ratio for sample size is calculated, participants are randomly selected for the sample
   • Identified strata doesn't account for all the differences within the target population

5. Opportunity Sample

   • Samples consist of anyone who is available and willing to participate
   • Convenient, cost and time effective
   • Prone to researcher bias based on characteristics of possible participants like appearance
   • Cannot be generalised because samples are drawn from a very specific area that is not fully representative of the whole target population

6. Volunteer Sample

   • Participants self-select
     • Researcher will produce an advert with the specific criteria
   • Less time consuming than other sampling methods
   • Prone to volunteer bias
     • Keen, helpful people are likely to volunteer
       • Less generalisable