Reliability of measurement scales Reliability, which is defined as the ratio of the true variance to the total variance, is an important property of measurement. In order to estimate the reliability, the concepts of measurement model and measurement scale are required. The model specifies the structure of the measurement, and the scale, which is a combination of the measured items, represents a realization of the theoretical notions. The reliability estimation is based on the general measurement framework introduced by Tarkkonen (1987) and further studied by Vehkalahti (2000), Tarkkonen & Vehkalahti (2005) and Vehkalahti & Puntanen & Tarkkonen (2007). 1 = Sucro /RELIAB (most typical measurement scales) 2 = RELIAB operation (any given measurement scales) 3 = Examples 4 = References M = More information on factor analysis and other multivariate analyses