. Author manuscript; available in PMC: 2017 Apr 1.

Published in final edited form as: Analyst. 2016 Mar 21;141(6):2053–2060. doi: 10.1039/c5an02387d

Table 2.

Accuracy and Precision of the method

	Theoretical Cortisol Concentrations (ng/ml)
	20.000	0.625
Within Day
Mean Measured Concentration (n=5)	20.422	0.628
Standard Deviation	0.504	0.061
Precision (%RSD)	2.5%	9.7%
Accuracy (% difference)	2.1%	0.5%
Between Day
Mean Measured Concentration (n=15)	21.420	0.531
Standard Deviation	2.631	0.099
Precision (%RSD)	12.3%	18.7%
Accuracy (% difference)	7.1%	−15.1%
Extraction Recovery (%, n=5)	97	103
Matrix Spike Recovery (%, n=3)	92

Precision is expressed as % RSD: (standard deviation)/(mean measured concentration)x100; Accuracy is expressed as % difference: [(measured-theoretical conc)/theoretical conc]x100.