Types of sampling

single-blind technique

when information about the study is withheld from participants

double-blind technique

when the aims of the study are withheld from both participants and researchers

random sampling

a technique used to gather a random sample of participants from the target population

stratified sampling

a technique that ensures subgroups of the target population are proportionately represented in a sample

volunteer sampling

a technique that asks for participants by placing an advert for volunteers

biased sample

when the sample recruited is made up of a particular type of person, which may not reflect the target population

opportunity sampling

a technique that recruits participants who are readily available at the time

independent measures design

participants are split into groups, with each group tested in only one condition of a study

repeated measures design

the same participants are used in all conditions of a study

matched pairs design

different participants are used in each condition of the study, but are matched for the likeness on important characteristics

reliability

the consistency of an outcome or result on an investigation (a measure)

validity

whether the test measures what was intended

internal validity

whether the measures used in a test genuinely test what they were designed to test

external validity

whether the findings are generalisable to the target population