IB psych unit 2

validities and types of samples

construct validity

the extent to which an experiment measures the construct it is designed to measure

operationalism

to make something measurable

internal validity

the extent which a study can show a cause and effect relationship, if results can be attributed due t change in IV (minimum confounding variables)

internal validity experiment ex.

skateboarding example

higher internal validity

counterbalancing, placebo, double blind

lower internal validity

experimenter bias, lack of control, demand characteristics

external validity

can be applied outside of story(if results would be same in dif setting)

ecological validity

if the conditions reflect real world behavior

mundane realism

if experiment is low in ecological validity

population validity

the extent in which is applicable to a large population beyond pop sample

sample

participants being used in research/ experiment

target population

the ppl in which the finding can be generalized

random sample

equal chance of being picked

stratified sample

divide population from strata and selects from there while staying true to proportional population

self selected

participants who volunteered for study (advertisements)

opportunity/convenience sample

participants from easy to reach place for researcher (classroom)

judgemental/purposive sample

selected based on qualities needed for testing of experiment (in qualitative experiments)

snowball sample

existing participants recruit next particiapnt’s

strengths for opportunity sample

easy, cost effective

weakness for opportunity sample

potential bias

strength for random sample

less bias possible

weakness for random sample

leaves out some hard to reach population (unrepresenattve)

self selected strength

easy, able to do ethically questionable experiments

self selected weaknesses

selection bias (only ppl who volunteered doesn’t show all of pop),overrepresentation skews, lack of control

stratified strength

more representative of pop, higher accuracy

stratified weakness

complex, time consuming to list

snowball strength

cost effective(no need for adds), finds hard to reach population

snowball weakness

selection bias

purposive strength

good for qualitative research to find a trend

purposive weakness

researcher bias