What Is Reliability?
Reliability refers to the consistency of a measure. A test is considered reliable if we get the same result repeatedly. For example, if a test is designed to measure a trait (such as introversion), then each time the test is administered to a subject, the results should be approximately the same. Unfortunately, it is impossible to calculate reliability exactly, but there several different ways to estimate reliability.

Types of Reliability
There are four general classes of reliability estimates, each of which estimates reliability in a different way. They are:

Inter-Rater or Inter-Observer Reliability                                      Test-Retest Reliability
Parallel-Forms Reliability [comming soon]                                      Internal Consistency Reliability [comming soon]

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