Measurement reliability is important in any kind of research. It is defined as any measurement that is consistent and dependable. No measurement score is 100% true. Therefore, we can go further and say measure = true score+ error.

Inter-rater reliability only applies to situations/ studies when there are raters or judges. This concept identifies that that raters’ scores should not differ dramatically and there should be some sort of consistency on average.

Internal consistency reliability concerns assessment items or questions and that they should be similar with one another throughout the assessment.

Test re-test reliability is the reliability of an assessment to produce similar scores the next time you take it. An example would be a college assessment test (ACT,SAT). You would expect to get similar results if you take the ACT or SAT over again.