Statistics

Statistics Window Items

The Statistics window gives the operator a current reading of relevant numerical information.
The following items will be found in the Statistics window:

• Subgroup number (k).
• n = ObsCnt = Observation Count = number of individual observations made.
• XDBar = = X -double bar = the mean of the subgroup averages.
• Rbar = average of the subgroup ranges.
• s (all) = s
  

  s =

  = current standard deviation of inspection run

• RBar/d2 = estimated standard deviation
• Min = minimum observation value
• Max = maximum observation value
• Mean +/- 3,4,6s = control limits for XBar chart

• Defect Ratio = percentage of measurements outside of tolerance
• PPM = parts per million outside of tolerance

• Cp = potential process capability index = (UTL-LTL)/6s where s = RBar/d2
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• Cpk = potential process performance index = Zmin/3 where Zmin = min {(UTL – )/s, ( – LTL)/s}, where s = RBar/d2
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• CR = capability ratio = 1/Cp
• CPL = ( – LTL)/3s, where s = RBar/d2
• CPU = (UTL – )/3s, where s = RBar/d2
• Pp = actual process capability index = (UTL-LTL)/6s,  where s =
• Ppk = actual process performance index = Zmin/3 where Zmin = min {(UTL – )/s, ( – LTL)/s}, where s =