Quantifying Repeatability Reproducibility Sources of Error and Capacity of a Measurement: Demonstrated Using Laboratory Soil Plasticity Tests

Table 7

Repeatability and reproducibility results reported in ASTM D4318 and determined by two-way ANOVA-based analysis for the various laboratory tests.

Parameters	Liquid limit		Plastic limit		Bar linear shrinkage
	Casagrande cup	Fall cone	ASTM roller^b	Fall cone
Repeatability and reproducibility (R&R) reported in ASTM D4318^a
Single-operator standard deviation (%); (within-laboratory repeatability)	0.5	NA	0.3	NA	NA
Multilaboratory standard deviation (%); (between-laboratory reproducibility)	1.3		0.9
Two-way ANOVA-based R&R Analysis Results
(%)	0.6	0.5	0.4	NA	0.6
	30	30	24		30
95% confidence interval (%)	0.5–0.8	0.4–0.6	0.3–0.5		0.5–0.9
(%)	1.7	0.5	0.6		0.7
	6	3	5		3
95% confidence interval (%)	1.1–3.8	0.3–1.7	0.4–1.5		0.4–2.7
(%)	1.8	0.7	0.7		1.0
	8	10	11		10
95% confidence interval (%)	1.3–3.5	0.5–1.1	0.5–1.2		0.7–1.7
Fraction of due to	11	50	27		43
Fraction of due to	89	50	73		57

^aThe R&R analysis was conducted on a USCS: ML soil. ^bThe ASTM PL test was conducted on four samples, because the 0% bentonite sample was nonplastic.