n n - 2
Σ Xi Σ (Xi-X)
- i=1 i=1 1 / 2
(Mean) X ═ ---------------- ; S.D. ═(----------------- )
N N
N: number of measured value
S.D. Measured value
C.V. = ----------- X 100% ; Accuracy = ------------------- X 100%
Mean Theoretical value
(3) Accuracy value must be 99-101 % and C.V. value must be less than 1 %.