Central Line
lnCentralLine=lnTotalDef/lnTotalComp, where lnTotalDef is sum of all defect quantities * 1000000 and lnTotalComp is sum of inspected quantities*Parts Per Unit (entered in the routing module)
At this time system will decide if it can use average group size or not. If the size group varies more tan 15% the system will use variance Upper and Lowercontrol limit. If average group size could be used the average group size gets calculated by taking lnAvrgSubgrSize=lnTotalComp divided by number of groups and rounded to the nearest integer.
Calculation for the Upper Control Line
LnUpperLine=ROUND(((3*(SQRT(lnCentrLine*(1000000-lnCentrLine))))/SQRT(lnAvrgSubgrSize)),3)
Calculation for the Lower Control Line
lnLowerLine = ROUND(lnCentrLine -((3*(SQRT(lnCentrLine*(1000000-lnCentrLine))))/SQRT(lnAvrgSubgrSize)),3)
lnLowerLine = IIF(lnLowerLine<0,0,lnLowerLine)