Data entered with different subgroup sizes for one standard

 

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Entering data with a different subgroup size

If you need to change the number of samples per subgroup, you can change the subgroup size used to store data for a standard, using one of these methods:

Real-time checks based on most recent data group

When data is grouped, real-time checks will be based on the control limits from the most recent group. This applies even if control limits are not displayed.

Because real-time control limits are calculated from the historical data in the new data group, you may need to enter the minimum number of subgroups needed to recalculate control limits or refresh the data before new control limits can be calculated and used for real-time checking on this new data group.

Analyzing data with different subgroup sizes

Different subgroup sizes on one chart

Depending on your configuration settings for varying subgroup sizes, GainSeeker may group the data according to its effective subgroup size—the number of numeric data values in the subgroup.

When the number of numeric values in one subgroup is different from that of the previous subgroup, this newer subgroup becomes the first point in a new data group.


In the example above:

Different subgroup sizes on a data table

When displaying data that was stored with different subgroup sizes, a data table will display enough Data columns to accommodate the largest subgroup size retrieved— regardless of the subgroup size currently set in the standard.

This data table displays data records stored with a subgroup size of three, followed by data records stored with a subgroup size of four. The table displays four Data columns because the largest subgroup size in this data retrieval is four.

However, when the retrieval contains only data that was stored with a subgroup size of three, the data table displays only three Data columns:

Analysis when data values > subgroup size

In the very rare event that the number of numeric data values in a record is greater than the subgroup size that was stored for that record, different analysis modules will function differently:

Can I change the subgroup size of a stored data record?

You should set the correct subgroup size before storing data.

The only way to change the subgroup size of a stored data record is to use the SQL Utility or a similar program to change this value in your data table. This type of database operation should only be attempted by your database administrator after ensuring that a recent backup of this table can be easily restored if a problem occurs.

Incomplete subgroups or a different subgroup size?