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

## Conclusions and Next Step

Conclusions The goals of this case study were:
1. Determine the most important factors.
2. Determine the best settings for the factors.
3. Determine a good prediction equation for the data.
The various plots and analysis showed that the number of turns (X1) and the winding distance (X2) were the most important factors and a good prediction equation for the data is:

$$\hat{Y} = 2.65875 + 1.55125 X_{1} - 0.43375 X_{2}$$

The DOE contour plot gave us the best settings for the factors (X1 = -1 and X2 = 1).

Next Step Full and fractional designs are typically used to identify the most important factors. In some applications, this is sufficient and no further experimentation is performed. In other applications, it is desired to maximize (or minimize) the response variable. This typically involves the use of response surface designs. The DOE contour plot can provide guidance on the settings to use for the factor variables in this next phase of the experiment.

This is a common sequence for designed experiments in engineering and scientific applications. Note the iterative nature of this approach. That is, you typically do not design one large experiment to answer all your questions. Rather, you run a series of smaller experiments. The initial experiment or experiments are used to identify the important factors. Once these factors are identified, follow-up experiments can be run to fine tune the optimal settings (in terms of maximizing/minimizing the response variable) for these most important factors.

For this particular case study, a response surface design was not used.