Sampling Flashcards
Who is the target population
- the group of people from whom the sample is draw
- e.g. if the sample of pps is taken from sixth form schools in salisbury, the findings of the study can only be applied to that group of people
Why do psychologists use sampling techniques
- to choose poeple who are representative of the population as a whole
- if your sample is representative then you can generalise the results of your study to the wider population
What is opportunity sampling
- taking the sample from people who are available at the time the study is carried out, and fit the criteria you are looking for
- most used by psychology students
Advantages of opportunity sapling
- quick and practical way of getting a sample
- natural expereiments have to be used as the researcher has no control over who is studied
Disadvantages of opportunity sampling
- unrepresentative-cannot be generalised to target population
- pps have the option to decline-so sample may then become self selected
What is random sampling
- every member of a population has an equal chance of being chosen
- identifying everyone in the target population and then selecting the number of pps you need in a way that gives everyone in the population an equal chance of being picked
- could be done manually e.g. using a hat, or computer e.g. randomly picking numbers
Advantages of random sampling
- unbiased selection-therefore more likely to be representative
- generalisation-if representative then results can be generalised to the target population
- everyone has an equal chance of being selected
Disadvantages of random sampling
- impractical-difficult to achieve and get full details of the target population. Not all will be available and some may not want to take part
- not representative-does not guarantee an unbiased sample
What is stratified sampling
classifying the population into categories and then choosing a sample which consists of pps from each category in the same proportions as they are in the populatoin
Advantages of stratified sampling
- unbiased selection-therefore more likely to be representative
- generalisation-if representative then results can be generalised to the target population
Disadvantages of stratified sampling
- knowledge of population characteristics required. May not be available
- time consuming
What is self selected (volunteer) sampling
- pps becoming part of a study because they volunteer when asked or in response to an advert
- researcher may then select those suitable for study
Advantages of volunteer sampling
- ease of formation-creating sample requires little effort
- less chance of the “screw you” phenomenon-pps are eager to take part so less chance of deliberate sabotage
- large number of people may respons so allows for more in depth analysis and more accurate results
Disadvantages of volunteer sampling
- unrepresentative-volunteers tend to be a certain “type” of person so cannot generalise to target population
- demand characteristics-volunteers are eafer to please so increases the chance of demand characteristics
What is systematic sampling
- taking the nth person from a list to create a sample
- e.g. if a company has a workforce of 1000 employees and a sample of 20pps is needed, then 1000÷20=50. Therefore take every 50th name from the list of employees to make a sample