Completing Incomplete Subgroups in QC-CALC Real-Time
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written: 05/11/2023
last modified: 04/08/2024

PREREQUISITES
QC-CALC 4.0+


INTRODUCTION

An issue we are asked about frequently is a situation where certain parts of a subgroup will never arrive and how to deal with it without inducing uneven subgroups.

So let's say the subgroup size is 5 and there are 15 records in the part file. The subgroups will therefore be records 1-5, 6-10, and 11-15. The operator is measuring 5 parts each hour but for whatever reason only gets 3 parts for measurement. These will write records 16, 17, and 18. The problem comes when the next group of 5 records arrive. Rather than creating 21-25 as expected, they will end up in positions 19-23 thereby offsetting every subgroup going forward and making a mess from a statistical standpoint.

To solve this, there are two options; the before and the after the fact solutions.


THE BEFORE STEPS

If the operator knows at the time it's happening, it is a relatively easy fix.

  1. Right click the last point in the plots and choose Complete Current Subgroup.


Continuing with the scenario above, QC-CALC RT will automatically insert two blank records in positions 19 and 20 allowing the next subgroup to continue in the correct 21-25 position. Note, that the blank records will be considered "excluded" and viewable as gold dots in the plots when viewing in individuals mode (View > Individuals Mode). In addition, any statistical calculation involving the subgroups will correctly exclude the "incomplete" subgroup from the list of subgroups.

THE AFTER STEPS

If the operator does not realize the issue has occurred until later, it's still a relatively easy fix.

  1. Choose Tools > Insert Blank Records.
  2. On the screen that appears, choose to insert 2 records after record 18 and click OK.


Continuing with the scenario above, QC-CALC RT will automatically insert two blank records in positions 19 and 20 and push the next subgroup to continue in the correct 21-25 position. Note, that the blank records will be considered "excluded" and viewable as gold dots in the plots when viewing in individuals mode (View > Individuals Mode). In addition, any statistical calculation involving the subgroups will correctly exclude the "incomplete" subgroup from the list of subgroups.



MORE INFORMATION

If the Tools > Insert Blank Records menu is disabled, it is because the subgroup at the part file level is currently set to Individuals (1). To change this, go to File > Properties > General Settings and change the subgroup size to something larger than 1.