Parts manufactured by an injection molding process are subjected to a compressive strength test. Twenty samples of five parts each are collected, and the compressive strengths (in PSI, pounds per square inch) were used to construct x-bar and R-control charts. The charts are then applied to an additional 15 samples of size five.  The specifications call for 80 PSI ± 5 PSI. The two data sets are as follows:

 83.0  81.2  78.7  75.7  77.0
 88.6  78.3  78.8  71.0  84.2
 85.7  75.8  84.3  75.2  81.0
 80.8  74.4  82.5  74.1  75.7
 83.4  78.4  82.6  78.2  78.9
 75.3  79.9  87.3  89.7  81.8
 74.5  78.0  80.8  73.4  79.7
 79.2  84.4  81.5  86.0  74.5
 80.5  86.2  76.2  64.1  80.2
 75.7  75.2  71.1  82.1  74.3
 80.0  81.5  78.4  73.8  78.1
 80.6  81.8  79.3  73.8  81.7
 82.7  81.3  79.1  82.0  79.5
 79.2  74.9  78.6  77.7  75.3
 85.5  82.1  82.8  73.4  71.7
 78.8  79.6  80.2  79.1  80.8
 82.1  78.2  75.5  78.2  82.1
 84.5  76.9  83.5  81.2  79.2
 79.0  77.8  81.2  84.4  81.6
 84.5  73.1  78.6  78.7  80.6
 
 68.9  81.5  78.2  80.8  81.5
 69.8  68.6  80.4  84.3  83.9
 78.5  85.2  78.4  80.3  81.7
 76.9  86.1  86.9  94.4  83.9
 93.6  81.6  87.8  79.6  71.0
 65.5  86.8  72.4  82.6  71.4
 78.1  65.7  83.7  93.7  93.4
 74.9  72.6  81.6  87.2  72.7
 78.1  77.1  67.0  75.7  76.8
 78.7  85.4  77.7  90.7  76.7
 85.0  60.2  68.5  71.1  82.4
 86.4  79.2  79.8  96.0  75.4
 78.5  99.0  78.3  71.4  81.8
 68.8  62.0  82.0  77.5  76.1
 83.0  83.7  73.1  82.2  95.3

(From D. Montgomery, Introduction to Statistical Quality Control, 4th ed.)

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