External validity is important in psychology studies - it measures the extent to which an experiment can be generalised to create general rules that can be applied in other, real life situations.
External validity helps in behavioural approaches, for example, in which psychologists attempt to understand a wider population's behaviour by studying a select sample of participants for an experiment.
Ensuring External Validity
In order for an experiment to possess external validity, the conditions must be comparable to real life situations. For example:
- Gender, age, etc.
If an experiment's participants are imbalanced in terms of factors such as gender and race, it lacks external validity in that it cannot be generalised to be applied to a population in which such make-up is different, as in turn, their behaviour may vary.
- Individual differences
Humanist approaches emphasise the difference in behaviour between each person. If a participant's background varies from that of a general population (for example, they suffer from a disorder) then the experiment cannot be generalised to people who do not possess such differences.
External versus Ecological Validity
Ecological and external validity are linked but different, and shouldn't be confused. External validity measures the extent to which findings can be generalised to real-life, while ecological validity measures the extent to which an experiment approximates real life.