VALIDITY

Internal validity

the extent to which the study is testing what it intends to test

the degree to which the observed change in the DV was the result of manipulation of the IV

ppt reactivity /effects

may lead to ppt changing the behaviour, making behaviour unnatural

screw U effect = ppts may deliberately under perform to sabotage the results of the study

demand characteristics = any cue from the researcher or from the research situation that makes ppt unconsciously aware of the aims of a study or helps ppts work out what the research expects to find

please U effect = may act in a way they think is expected and over perform to please the experimenter

social desirability bias

therefore may not behave in the way they usually do

often occurs in interviews or questionnaires

ppts may wish to present themselves in the best possible way

investigator effects

act as extraneous variables

any effect of the investigators behaviour on the research outcome

eg. design of the study, interaction with ppt

physical characteristics as well = age, gender, tone of voice

order effects

repeated measures

practice effect = the ppt becomes practiced at the task because they are doing it more than once, which leads to improved performance in the second condition

order in which the conditions are done may have an effects on the outcome

boredom effects = ppt becomes bored with the task

assessing validity

face validity

concurrent validity

established by using a rating scale to assess the suitability of the measure

the extent to which something looks like or appears to measure what it intends to measure

scores are then correlated

high correlation would indicate concurrent validity

comparing results of a new measure against the results of another measure (same behaviour) that has already established being valid

external validity

different places or settings (ecological validity)

different people or populations (population validity)

the extent to which the findings can be generalised beyond the study to...

different points in time (temporal validity)