Hach-Lange TENSETTE plus User Manual - Handbuch (Seite 30)

Calibration
30
5.5.2 Accuracy (systematic error)
Accuracy is the difference between the dispensed volume and the
selected volume of a pipette..
Accuracy can be expressed as a relative value:
5.5.3 Precision (random error)
Precision refers to the repeatability of the pipettings. It is expressed
as standard deviation (s) or coefficient of variation (cv).
Standard deviation can be expressed as a relative value (cv).
A = V - V
0
A = accuracy
V = mean volume
V
0
= nominal volume
A% = 100% x A / V0
s = standards deviation
V
¯ = mean volume
n = number of measurements
cv = 100% x S / V ¯
S =
V
i
V – ( )2
n 1 –
---------------------------------
n
Σ
i=1