POPULATIONS, SAMPLES, SAMPLING METHODS Flashcards
Target population
Group of people psychologists want to be able to generalise their findings to.
Psychologists need to take sample of people who are reflective of target population wanting to be studied.
Sampling
Selecting ps from population, should be representative of target population, the more representative, the more confident researcher can be that results can be generalised to target population.
Problems with generalisability
Only studying people from one area.
May be bias in age ( too many old or young )
More men than women ( gender bias ) May only be reflective of one ethnic origin.
Gender bias
Sample made of people from one gender, not representative of all.
Androcentric
Biased towards men, all male sample.
Estrocentric
Biased towards women, all female sample.
Cultural bias
Sample too focused on one culture, not representative of all cultures.
Ethnocentric
Sample biased to one culture/ ethnicity.
Population validity
Can we generalise results from our sample to target population?
4 Sampling methods
Opportunity
Self-selected (volunteer)
Random
Snowball
Opportunity sampling
Easiest, most common, cheapest.
Using people readily available to you, willing to partcipate.
Strengths of opportunity
-easiest, quickest
-most economical, cheap
-easy access to psychologist
-only sampling method for some research methods (covert= undercover experiment/observation)
Weaknesses of opportunity
-likely to produce biased sample
-only certain types of people selected from limited geographical areas
-not representative
Self-selected/ volunteer sampling
People who want to take part volunteer themselves.
Psychologist places advert such as a poster or a flyer, those interested reply and psychologist filters responses to collect sample reflecting their target population.
Then contact ps to take part.
Strengths of volunteer
-target/request ps who may have features required for investigation
-convenient and ethical, informed consent
-people more likely to be committed, no sample attrition.
Weaknesses of volunteer
-unrepresentative-leads to biased sample
-no responses to advert unless they have a strong interest or view.
-demand characteristics likely (act accordingly to aim)
Random sampling
Every member of target population has equal chance of being selected.
Names needed of all members of target population, all potential ps are entered into a draw, names are randomly selected until desired number of ps is chosen.
Random name/ number generator can be used.
Ps then contacted to take part.
Strengths of random
-least biased method, all members of target population equal chance of selection
-representative sample of target population
Weaknesses of random
-difficult and time consuming to do
-harder to do with larger target populations
-Representative sample not always guarenteed.
Snowball sampling
Used if population not easy to contact, achieved by asking a ps to suggest someone else who may be willing to take part/ appropriate for study.
Useful in hard to obtain populations; drug users, truants etc…
Strengths of snowball
-possible to access members of groups where no lists/ identifiable clusters even exist e.g criminals.
-good to gather samples of groups hard to access
Weaknesses of snowball
-can be slow process, time consuming
-no way of knowing if sample is representative as ps are usually friends of friends.
