SAMPLING

• Target population – large group of people that the research wants to focus on 
• Sample – smaller group of people who are representative of the target population 
• Sampling bias – when a specific group of people are over or underrepresented in the sample 
• Random sampling - When all participants have an equal chance of selection 
• How to conduct random sampling

  List of names in the target population 

  Give each name a number 

  Computer programme will pick out numbers at random 
• Strengths of random sampling:

  No researcher bias as everyone has an equal chance 

  Weaknesses of random sampling:

  Time consuming  

  May end up unrepresentative  

  Those selected may refuse to take part  
• Systematic sampling - Where every Nth person is picked  
• How to conduct systematic sampling:

  Produce a sampling frame  

  Decide which Nth it will be 

  Pick out selected participants 
• Strengths of systematic sampling:

  No researcher biases 

  Usually representative 

  Weaknesses of systematic sampling:

  Time consuming 

  Refusal to take part 
• Stratified sampling - Sample is representative of the people in the subgroups (strata) of target population 
• How to conduct stratified sampling:

  Identify subgroups 

  Calculate the proportions needed  

  Use random technique to select members for subgroup 
• Strengths of stratified sampling:

  No researcher bias. 

  Representative so generalisation is possible 

  Weaknesses of stratified sampling:

  Stratification is not perfect – does not reflect all differences so complete representation is not always possible 
• Opportunity sampling - Researcher selects anyone willing at the time 
• Strengths of opportunity sampling:

  Easy – saves time and money 

  Weaknesses of opportunity sampling:

  Unrepresentative as drawn from a small area 

  Researcher bias – may avoid asking certain people or may only attract certain people 
• Volunteer sampling - a sample is selected by the researcher from a group of people who have volunteered to take part in the study
• How to conduct volunteer sampling:

  Place an advert somewhere 

  Alternatively asking a group of people and see who raises their hand 
• Strengths of volunteer sampling:

  Easy – participants come to you 

  Motivated by reward 

  Weaknesses of volunteer sampling:

  Volunteer bias – only attracting a certain group of people 
• Rachel Seeks Volunteers Or Stamps