Zusammenfassung der Ressource
validity
- types of validity
- internal validity
- 3 challenges of internal validity
- The cause and effect must be related
- cause must precede effect
- The cause must be the only factor responsible for the effect
- indicates if results reflect experimental manipulation of iv
- did the IV cause an effect in the DV
- poor internal validity if
- There is an alternative explanation for the result
- Things other than the IV differ between groups
- Poor internal validity can be caused by a confounding variables
- threats to internal validity
- selection bias
- Having groups that were different from one another before the study began
- maturation
- Biological or psychological changes that occur due to maturation can include the dependent variable
- repeated testing / sequence effect
- When the administration of a task early in the study affects performanceon a later task
- regression to the mean
- Extreme scores on a DV will tendto be less extreme when they are assessed again
- history
- Historical events that occur during the course of a study can influence the DV
- instrumentation
- The scoringof an instrument might change over time and this changes scores on the DV
- attrition
- loss of participant, ie drop out, death
- Diffusion of treatment
- Information a participant has learned about a study (from other participants) influences
their behaviour when they participate
- subject effects
- The participant influences the effects observed in the DV ie placebo
- experimenter effects
- treating groups differently
- construct validity
- Whether the manipulation or measurement is related to the underlying
psychological construct it should be
- face validity
- extent to which a manipulation or measure looks, on the face of it, to be valid
- convergent validity
- extent to which different measures or manipulations of the same construct are related(correlated)
- Correlate your measure with another measure that has already been shown to possess high
construct validity
- discriminative validity
- the extent to which measuresor manipulations of different constructs are unrelated(not correlated
- Show that your measure gives different outcomes from a measure of a different construct
- Content validity
- extent to which a measure represents a balanced and adequate sampling of the relevant construct
- important for multiple question construct Ask an expert if the items assess what you want them to
assess
- external validity
- Indicates the extent to which the results of a study can be
generalised to other people, conditions, places and time
- Mainly concerns the participant and testing situation
- Threats to external validity
- Poor selection of participants
- Participant selection involves the correct sampling of participants
and the assignment of participants to treatment conditions
- Your sampling will determine the population to which your results will generalise
- Pre-test sensitisation
- When the presence of a pre-test condition changes the effectiveness
of the subsequent treatment
- If treatment is repeated without the pre-test, different results occur
- Multiple treatment interference
- Participants receive an unintended treatment in addition to the intended
treatment
- statistical validity
- How appropriate were the statistical methods that were used
- When an experiment actually tests the hypothesis you want it to test
- Whether a method actually measures what you intend it to measure