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A Graphical Aid for Analyzing Autocorrelated Dynamical Systems 461

Yarian SPC data extracts

Figurę 22. Phase map movie extracts from the Varian SPC data. The plot on the right is an extract around observation 320 and the plot on the left is an extract around the observation 260.

Yarian SPC data extract

Figurę 23. A morę typical extract from the univariate phase map movie of the Yarian SPC sputterer data.

It is apparent from this data set and the accompanying traditional plots used with time senes models that the likelihood of any analyst involved in a typical modeling setting would have completely missed two real, dramatic, high signal (Iow noise) changes in the underlying process. An interesting side notę is that the operators were able to actually control the process better during at least one of the wear-out periods — indicating in this case there might be substantial process control improvement with continual process intervention.