Before reading this section, make sure you understand:
In psychological measurement, reliability refers to the repeatability or consistency of a measure.
We commonly describe cars, for example, in terms of their reliability. A reliable car is one which starts every time ignition is attempted. An unreliable car doesn't start all the time.
There are two main types of reliability which are commonly examined in psychological measurement:
- Internal consistency (Internal reliability): Correlation amongst the items used in a multi-item measurement scale?
- Test-retest reliability: Correlation between scores on the same measure by the same participants at different times
- Inter-rater reliability: Correlation between scores by different raters (observers); for observational measures