Table 7.

The Uncertainty budget for pH of PVP-I solution.

Sources of uncertainty	Unit	Value (x)	Uncertainty (u(x))	Coverage factor (k) (95% CI)	Relative uncertainty (u(x)/x)
0.5% PVP-I solution
Balance	g	5	0.002	2	0.0002
V. Flask	mL	1000	0.24	2	0.00012
M. Cylinder	mL	167	0.36	2	0.0011
pH Meter	–	4.86	0.002	2	0.00021
Homogeneity	–	4.896	0.002	–	0.00041
Stability	–	4.86	0.012	–	0.0025
Repeatability	–	4.86	0.02	–	0.0041
				Mean value	4.86
			Combined standard uncertainty		0.024
			Coverage factor (95% CI)		2
			Expanded uncertainty		0.05
0.6% PVP-I Solution
Balance	g	6	0.002	2	0.00017
V. Flask	mL	1000	0.24	2	0.00012
M. Cylinder	mL	167	0.36	2	0.0011
pH Meter	–	4.82	0.002	2	0.00021
Homogeneity	–	4.919	0.003	–	0.00061
Stability	–	4.82	0.0069	–	0.0014
Repeatability	–	4.82	0.02	–	0.0041
				Mean value	4.82
			Combined standard uncertainty		0.02
			Coverage factor (95% CI)		2
			Expanded uncertainty		0.04