Reliability (in assessment/evaluation)
DEFINITION 1: Reliability is concerned with the consistency and dependability of a measuring instrument, that is, it is an indication of the degree to which it gives the same answers over time, across similar groups and irrespective of who administers it. A reliable measuring instrument will always give the same result on different occasions assuming that what is being measured has not changed during the intervening period. Inter-rater reliability is a measure of the consistency between the ratings or values assigned to an observed phenomenon and is employed by researchers using structured observation techniques; it is usually expressed as a percentage of agreement between two raters.
SOURCE: Hickman, Richard (2013). Cambridge Handbook of Educational Abbreviations & Terms ( C.H.E.A.T.,.6th edition, Faculty of Education, University of Cambridge.
DEFINITION 2: One of the principles of assessment and refers to the consistency of the interpretation of evidence and the consistency of assessment outcomes. Reliability requires a standard benchmark of assessor competence and relevant vocational competence or access to subject matter expertise, and can only be achieved when assessors share a common interpretation of the unit/s being assessed.
SOURCE: IBSA (2015). VET Glossary. Part of a suite of support materials for the TAE Training and Education Training Package. 4th Edition, Australia.