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5. Process Improvement
5.6. Case Studies
5.6.1. Eddy Current Probe Sensitivity Case Study

Intermediate Conclusions

Important Factors Taking stock from all of the graphical and quantitative analyses of the previous sections, we conclude that X1 (number of turns) is the most important engineering factor affecting sensitivity, followed by X2 (wire distance) as next in importance, followed then by some less important interactions and X3 (wire gauge).
Best Settings Also, from the various analyses, we conclude that the best design settings (on the average) for a high-sensitivity detector are
    (X1,X2,X3) = (+,-,+)
that is
    number of turns = 180,
    winding distance = 0.38, and
    wire gauge = 48.
Can We Extract More From the Data? Thus, in a very real sense, the analysis is complete. We have achieved the two most important stated goals of the experiment:
  1. gaining insight into the most important factors, and

  2. ascertaining the optimal production settings.
On the other hand, more information can be squeezed from the data, and that is what this section and the remaining sections address.
  1. First of all, we focus on the problem of taking the ranked list of factors and objectively ascertaining which factors are "important" versus "unimportant".

  2. In a parallel fashion, we use the subset of important factors derived above to form a "final" prediction equation that is good (that is, having a sufficiently small residual standard deviation) while being parsimonious (having a small number of terms), compared to the full model, which is perfect (having a residual standard deviation = 0, that is, the predicted values = the raw data), but is unduly complicated (consisting of a constant + 7 terms).
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