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Inner Diameter of Landing Gear Triunion

Keywords: time series, sum of sinusoids, discrete spectra, control chart


The data give 29 consecutive measurements on the inner diameter of a landing gear triunion. Each value given here is the average of four original observations.

Variable Description

Diameter Average inner diameter


Data File (tab-delimited text)


Cowden, D. J. (1957). Statistical Methods in Quality Control. Prentice-Hall, Englewood Cliffs.

Spurrier, J. D., and Thombs, L. A. (1990). Control charts for detecting cyclical behavior. Technometrics 32, 163-170.

Smyth, G. K. (2000). Employing symmetry constraints for improved frequency estimation by eigenanalysis methods. Technometrics 42, 277-289.


Spurrier and Thombs (1990) showed that the data show some evidence of periodic behavior, which is one way that a process can be out-of-control. Here we fit one sinusoidal signal to the data.

diameter.gif (4518 bytes)



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