What are the numerous measures for reliability assessment of a scale?

Answer

Reliability in research relates to consistency of results over a period of time. A scale is called reliable if it produces consistent results when repeated measurements are made. As name suggests, in test-retest reliability measurement, same respondents are administered identical sets of scale items at two different times (generally 2 - 4 weeks). Degree of similarity between measurements (measured through correlation between both measurements) determines the reliability. The higher the correlation between two measurements, the higher the scale reliability. In measuring alternative forms reliability, two equivalent forms of scale are constructed and then same respondents are measured at two different times.