Sampling Flashcards
What is Sampling?
- This is the process used by psychologists to choose this group of people
- Individuals who take part in research are called participants and are a small group of people
What is the target population?
- This is the group of individuals researcher wishes to investigate
- Must be enough to make generalisations
What are the sampling techniques?
- Random
- Opportunity
- Volunteer
- Stratified
- systematic
What is Random Sampling?
- Where all participants have an equal chance of being elected and are chosen without any bias
- Obtained Through either Computer selection or Manual Selection
What is Computer Selection?
- A computer generating an endless string of numbers and then assign a number to a participant and a random number generator produces numbers to use in the target population
What is Manual Selection?
- Using paper and placing them in a container, hat or bowl etc.
- Container should be shaken each time a piece is drawn
- All prices of paper information should be folded up the same amount and way
What is a strength for Random Sampling?
Every member of population has equal opportunity
- Researcher selected the sample without bias or participants being cherry picked
What are 2 weaknesses for Random Sampling?
Sample may not represent
- Even tho researcher hasn’t enforced ant kind of bias it may still lead to a sample that unrepresentative
- Male:Female ratio may not represent target population
Time - Consuming
- Very time consuming for researcher to assign all participant with a number and to then further do it manually
What is volunteer sampling?
- Sampling where participants volunteer themselves to make up the sample
How is volunteer sampling done?
- Usually done by using advertisements or posters which are placed in an area which will be accessible and visible to the target population
What is a strength of Volunteer sampling?
No problems with consent
- Volunteers are stepping forward to volunteer themselves so have already consented
What are 2 weakness of Volunteer sampling?
Problems with volunteer bias
- Likely to be highly motivated and have extra time on their hands and less likely to be apart of the target population
Low response rate lead to unrepresentative sampling
- Unlikely to respond to requests to participate in the study
- The data gathered from this sample are also unlikely to be represented so cannot make generalisations
What is Opportunity Sampling?
- Sample made up of participants who are readily available at the time of the study
How do we obtain opportunity sampling?
- Simply by asking people off the street to the areas we want to use the target population from
What are 2 weaknesses of Opportunity sampling?
Researcher Bias
- Runs the risk of the researcher asking specific people over others
- Might use individuals who they thing will be better than others
Not everyone has a chance of selection
- Asking those on the streets of a town may be ignore those who are at work or live in rural areas
- Not representative
What is Systematic sampling?
- Using a pre-determined system where every nth ( N = Number, like every 5th person or every 7th person) member of the target population is selected
How do we obtain Systematic Sampling?
- Using a sampling frame, EG = every 5th Student on a register or every 3rd House on a street
- Reduces bias
What is a strength and a weakness of systematic sampling?
Avoids researcher bias
- Once systematic selection has been est. the researcher has no influence over those involved in the experiment
Sample still unrepresentative
- Still a chance that the sample will not represent the entire target population
- Possible to still only sample only males
What is Stratified sampling?
- Small scale reproduction of the target population
- STRATA are sub groups of target population such as age, gender, social class, ethnicity
How do we obtain a stratified sample?
- If a target population has 60% females and 40% males then the stratified sample must also include these figures
- An experiment of Students and there are 100 in the target population 60 girls and 40 boys.
- Using a sample of 20 participants, if we want 60% girls and 40% boys we’d use 12 girls and 8 boys
What is a strength and a weakness of stratified sampling?
Results can be generalised to the target population
- More Likely to be representative of the target population as the participants are proportional and have been selected at random
Time Consuming
- Much more time consuming than other methods of sampling and can be expensive
