A study was designed and conducted in 1992 by the Economic and Statistical Analysis Staff of the Cotton Division, AMS, USDA, to determine the principle components of variance in High Volume Instrument (HVI) measurements of micronaire, length, strength and length uniformity. HVI models included in the study were Spinlab 900-B, 900-C and 900-Automatic and Motion Control, Incorporated, (MCI) 3500 and 4000.

The study was conducted in three phases. Succeeding phases examined the components of variance of the principle component of variance from the preceding phase. Phase I revealed that instrument is the principle identifiable source of variability for all measurements. Phase II showed calibration level is the principle source of variability for length and strength in all three Spinlab models. Instrument/calibration level interaction is the principle source of variability for micronaire and uniformity in all models and for length and strength in the two MCI models. Phase III revealed slope was the principle component of variance within calibration for length and strength in all three Spinlab models, with offset also contributing significantly.