Table 3.

Uncertainty components for the DI determination of microsphere number concentration N.

Uncertainty component
Type A relative standard uncertainty	0.6 %
Type B components
Single/multiple microsphere variation	0.5 %
Broken or missed tracks	0.2 %
Undersizing of microspheres	0.3 %
Transfer and handling	0.5 %
Total type B relative standard uncertainty	0.8 %
Combined relative standard uncertainty, ur,c	1.0 %
Effective degrees of freedom	16
Coverage factor for 95 % confidence level	2.1
Expanded relative uncertainty (k = 2)	2.0 %
Expanded relative uncertainty (95 % confidence level)	2.1 %