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Tensile Strength of Welds

Keywords: fractional design, Taguchi design, two-level design, dispersion effects.


This is a highly fractionated two-level factorial design employed as a screening design in an off-line welding experiment performed by the National Railway Corporation of Japan. There were 16 runs and 9 experimental factors. The response variable is the observed tensile strength of the weld, one of several quality characteristics measured. All other variables are at plus and minus levels.

Variable Description

Rods Kind of welding rods
Drying Period of drying
Material Welded material
Thickness Thickness
Angle Angle
Opening Opening
Current Current
Method Welding method
Preheating Preheating
Strength Tensile strength of the weld in kg/mm


Data File (tab-delimited text)


Taguchi, G., and Wu, Y. (1980). Introduction to Off-Line Quality Control. Central Japan Quality Control Association, Nagoya, Japan.
Box, G. E. P., and Meyer, R. D. (1986). Dispersion effects from fractional designs. Technometrics 28, 19-27.
Carroll, R. J., and Ruppert, D. (1988). Transformations and Weighting in Regression.Chapman and Hall, New York, pages 107-110.
Bergman, B., and HynÚn, A. (1997). Dispersion effects from unreplicated designs in the 2k-p series. Technometrics 39, 191-198.
Nelder, J. A., and Lee, Y. (1998). Letter to the Editor: Joint modeling of mean and dispersion. Technometrics 40, 168-171.
Huele, A. F., and Engel, J. (1998). Response to Nelder and Lee. Technometrics 40, 172-175.
Smyth, G. K., Huele, F., and Verbyla, A. P. (2001). Exact and approximate REML for heteroscedastic regression. Statistical Modelling: An International Journal. Volume 1 #3. To appear. (Zipped Postscript).


> jDrying <- jitter(Drying,factor=3)
> plot(jDrying,Strength,type="n",xlab="Drying")
> points(jDrying[Material==-1],Strength[Material==-1],col=2)
> points(jDrying[Material==1],Strength[Material==1],col=4)



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