The optional Ppk element is the performance index over all subgroups taking into account distribution centering on nominal corresponding to the "PPK" StatsValuesEnumType enumeration.
<xs:element name="Ppk" type="StatsMeasuredDecimalType" substitutionGroup="NumericCharacteristicWithTolStatsValue"><xs:annotation><xs:documentation>The optional Ppk element is the performance index over all subgroups taking into account distribution centering on nominal corresponding to the "PPK" StatsValuesEnumType enumeration.</xs:documentation></xs:annotation></xs:element>