The Effects of Using Shewhart Control Charts to Monitor the Strength and Length Operating Levels of High Volume Instruments

G. L. Lewicki, G. R. Faia, M. H. Fairley, and B. H. Robles


Shewhart control charts can be used, in theory, to monitor High Volume Instrument (HVI) operating levels. An experiment was conducted using numerous, randomly selected test and control instruments in three USDA, AMS, Cotton Division cotton classing laboratories to determine the effect of the use of control charts on HVI strength and length measurements. Adapted Shewhart control charts were used to monitor operating levels in test instruments. Test instruments were calibrated only when out of statistical control. Control instruments were operated per normal Cotton Division procedures. Data from both the test and control instruments were collected, analyzed and compared. Accuracy, precision and reliability indicators of classification data were not significantly affected by the use of control charts; however, the consistency of all was enhanced. Productivity was improved and the number of calibrations reduced. Therefore, control charts are applicable and effective for monitoring HVI operating levels.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pp. 1429 - 1432
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998