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Defects Per Unit

Inspections for defects per unit count the number of defects that occur on a specified number of units of product.  It is possible that more than 1 defect could occur per unit of product.  An alternative to counting the number of defects per unit is to count the number of defective units.

The types and sources of sampling plans for defects per unit are:
  • Single
  • Double
  • Multiple
  • ANSI Z1.4
     
    Many prefer to use the term nonconformity to clarify that failure to meet a requirement does not necessarily imply that the unit of product is unfit for use.  For example, a requirement may have been set for a particular dimension.  Passing the requirement ensures proper assembly of the parts.  But failure to meet requirements does not imply the parts will not assemble properly.  It only means that proper assembly cannot be guaranteed.