Q3. Explain the concepts of reliability, validity and sensitivity.
Answer. It is important to ensure that the instruments (for example, tests, questionnaires, etc.) used in program evaluation are as reliable, valid and sensitive as possible. According to Rossi et al. ,’a measure that is poorly chosen or poorly conceived can completely undermine the worth of an impact assessment by producing misleading estimates. Only if outcome measures are valid, reliable and appropriately sensitive can impact assessments be regarded as credible’.
Reliability
The reliability of a measurement instrument is the ‘extent to which the measure produces the same results when used repeatedly to measure the same thing’ (Rossi et al., 2004, p. 218).[6] The more reliable a measure is, the greater its statistical power and the more credible its findings. If a measuring instrument is unreliable, it may dilute and obscure the real effects of a program, and the program will ‘appear to be less effective than it actually is’ (Rossi et al., 2004, p. 219).[6] Hence, it is
