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WinSPC Statistics and SPC Theory rss button
Articles deal with the statistics and calculations used by WinSPC, including general SPC theory
There were 6 articles found in this category:
  1. questionHow are the initial control limits calculated for attributes (when there is not any data)?
    If an attribute is configured to have calculated control limits, WinSPC will determine an intial set of control limits to use prior to the first time the limits are recalculated based on the data (by default, this will occur after the 25th subgroup). If the attribute has a fixed (or constant) lo ...

  2. questionWhat is the difference between the '.Mean' and '.Avg' statistics in the equation builder?
    In the WinSPC Equation Builder, the '.Mean' statistic refers to the plotted mean value of a specific subgroup (in other words, it is the mean of the samples associated with the subgroup). The '.Avg' statistic, on the other hand, refers to the running average of all subgroups for that variable.

  3. questionHow are control limits calculated for an attribute c-chart?
    A c-chart displays the total number of nonconformities for each lot. This chart is available in WinSPC to an attribute that is configured with an 'Attribute Counts' of 'Defects' (also referred to as a 'Defect List') and an 'Inspection Lot Size' set to 'Fixed' (a c-chart requires a constant lot ...

  4. questionHow are control limits calculated for an attribute u-chart?
    A u-chart displays the number of nonconformities per unit produced. This chart is available in WinSPC to an attribute that is configured with an 'Attribute Counts' of 'Defects' (also referred to as a 'Defect List'). An attribute displaying a u-chart in WinSPC (configured to recalculate the cont ...

  5. questionHow are control limits calculated for an attribute np-chart?
    An np-chart displays the number of nonconforming (defective) units. This chart is available in WinSPC to an attribute that is configured with an 'Attribute Counts' of 'Defective Units' and an 'Inspection Lot Size' of 'Fixed' (an np-chart requires that the lot size be constant). An attribute dis ...

  6. questionHow are control limits calculated for an attribute p-chart?
    A p-chart displays the percentage of nonconforming (defective) units. This chart is available in WinSPC to an attribute that is configured with an 'Attribute Counts' of 'Defective Units'. An attribute displaying a p-chart in WinSPC (configured to recalculate the control limits every 5 subgroup ...


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