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1. Exploratory Data Analysis
1.4. EDA Case Studies
1.4.2. Case Studies Ceramic Strength

Analysis of the Response Variable

Numerical Summary As a first step in the analysis, common summary statistics are computed for the response variable.
      Sample size  = 480
      Mean         =   650.0773
      Median       =   646.6275  
      Minimum      =   345.2940  
      Maximum      =   821.6540  
      Range        =   476.3600  
      Stan. Dev.   =    74.6383  
4-Plot The next step is generate a 4-plot of the response variable.

4-plot of the response variable

This 4-plot shows:

  1. The run sequence plot (upper left corner) shows that the location and scale are relatively constant. It also shows a few outliers on the low side. Most of the points are in the range 500 to 750. However, there are about half a dozen points in the 300 to 450 range that may require special attention.

    A run sequence plot is useful for designed experiments in that it can reveal time effects. Time is normally a nuisance factor. That is, the time order on which runs are made should not have a significant effect on the response. If a time effect does appear to exist, this means that there is a potential bias in the experiment that needs to be investigated and resolved.

  2. The lag plot (the upper right corner) does not show any significant structure. This is another tool for detecting any potential time effect.

  3. The histogram (the lower left corner) shows the response appears to be reasonably symmetric, but with a bimodal distribution.

  4. The normal probability plot (the lower right corner) shows some curvature indicating that distributions other than the normal may provide a better fit.
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