Variability, accuracy of all closed-loop tests for three different instruments (F, R, and I) and for all instruments.

Xmeas and Xexp (in ppm) are the means of the measured and expected instrument PP, and Vloop gives estimated mean loop volume (ml) (SD and SE have the same units as their respective variables). Coefficient of variation CV(%) = 100(SD/Xexp), standard error is SE = SD/√n.Xmeas与Xexp（单位：ppm）分别为仪器PP的实测均值与预期均值；Vloop为估算得到的平均回路体积（单位：ml）。标准差（Standard Deviation，SD）与标准误（Standard Error，SE）的单位与其对应变量一致。变异系数（Coefficient of Variation，CV）(%)=100×(SD/Xexp)，标准误SE=SD/√n。