Internal validity is a concept in psychology that refers to the degree of confidence that the causal relationship being tested exists and is trustworthy. It is one of two concepts, along with external validity, that help determine how trustworthy and meaningful the results of a study are. Internal validity is concerned with control and is largely determined by the studys experimental design and methods. It examines the extent to which systematic error or bias is present in the study, which can arise through selection bias, performance bias, and other factors. In other words, internal validity pertains to the soundness of results obtained within the controlled conditions of a particular study.
Some key points about internal validity in psychology include:
- Internal validity tests how likely it is that a treatment caused the differences in results that are observed.
- It is largely determined by the studys experimental design and methods.
- Internal validity is concerned with control and examines the extent to which systematic error or bias is present in the study.
- There are eight threats to internal validity: history, maturation, instrumentation, testing, selection bias, regression to the mean, social interaction, and statistical regression.
- Researchers can counter threats to internal validity by using randomization, blinding, and other techniques.
