Welding data set
The data give the results of an unreplicated experiment for factors affecting welding quality conducted by the National Railway Corporation of Japan (Taguchi and Wu, 1980, cited in Smyth et al., 2001). It is a toy example for heteroscedastic models and is also suitable for illustrating fit of overparameterized models.
data("welding")The data frame includes 16 observations on 10 variables:
response variable;
nine two-level factors.
The data were downloaded from http://www.statsci.org/data/general/welding.txt on 2014/08/19 and are consistent with those shown in table 5 of Bergman and Hynén (1997).
Bergman B, Hynén A (1997) Dispersion effects from unreplicated designs in the 2^{k-p} series. Technometrics, 39, 191–98.
Smyth GK, Huele AF, Verbyla AP (2001). Exact and approximate REML for heteroscedastic regression. Statistical Modelling 1, 161-175.
Taguchi G, Wu Y (1980) Introduction to off-line quality control. Nagoya, Japan: Central Japan Quality Control Association.
data("welding")
## toy example from Smyth et al.
fitme(Strength ~ Drying + Material,resid.model = ~ Material+Preheating ,data=welding, method="REML")
## toy example of overparameterized model
fitme(Strength ~ Rods+Thickness*Angle+(1|Rods),resid.model = ~ Rods+Thickness*Angle ,data=welding)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.