The reliability of a measurement x can also be defined quantitatively as: R x = V t / V x {\displaystyle R_{\text{x}}=V_{\text{t}}/V_{\text{x}}} where R x {\displaystyle R_{\text{x}}} is the reliability in the observed (test) score, x; V t {\displaystyle V_{\text{t}}} and V x {\displaystyle V_{\text{x}}} are the variability in ‘true’ (i.e., candidate’s innate performance) and measured test scores respectively.