Forum Discussion
Post PatronSPC Chart - Summary Table - Seeking Meaningful Targets/Variation icons.
Hi F_Reh ,
You can configure your SPC chart to meet your needs. The issues you're observing are common and stem directly from how SPC charts interpret your data. You can set unique centerlines, and the grey icons and zero-value limits you see are simply reflections of a stable process where the event being measured has not occurred in the historical data.
It's perfectly fine and standard practice to set a different Centerline value for each KPI in your table. Since each row represents a unique process, each will have its own distinct average or performance target. Setting these individually is the correct way to build your summary.
The grey icons in the Variation column indicate that your process is stable, or "in control." This means no statistically significant trends or shifts have been detected according to the chart's rules. The icon will only change to blue (a positive process shift) or orange (a negative shift) when a rule is triggered, such as a data point falling outside the control limits. If your process is genuinely consistent, seeing grey icons is the expected outcome.
Your control limits are appearing as 0.0 because they are calculated directly from your historical process data. If the Numerator values used for the calculation have all been zero, then the average rate is also zero. Since control limits are based on the average and the variation around it, a zero average with no variation results in zero-value limits. For example, the general formula is:
Limits = Average ± (Multiplier × Standard Deviation)If your average and standard deviation are both zero, the limits will also be zero. You'll need historical data with non-zero numerators to generate meaningful control limits.
A properly set Centerline (Target) is absolutely required for the chart's statistical functions, but an Alt. Target is not. The Centerline is the primary reference used to calculate the control limits and apply the rules that trigger the variation icons. In contrast, the Alt. Target is just an optional, visual reference line. It's helpful for comparing performance against a stretch goal or benchmark, but it does not influence any calculations or the variation icons.
Best regards,
Super UserHi F_Reh ,
You can configure your SPC chart to meet your needs. The issues you're observing are common and stem directly from how SPC charts interpret your data. You can set unique centerlines, and the grey icons and zero-value limits you see are simply reflections of a stable process where the event being measured has not occurred in the historical data.
It's perfectly fine and standard practice to set a different Centerline value for each KPI in your table. Since each row represents a unique process, each will have its own distinct average or performance target. Setting these individually is the correct way to build your summary.
The grey icons in the Variation column indicate that your process is stable, or "in control." This means no statistically significant trends or shifts have been detected according to the chart's rules. The icon will only change to blue (a positive process shift) or orange (a negative shift) when a rule is triggered, such as a data point falling outside the control limits. If your process is genuinely consistent, seeing grey icons is the expected outcome.
Your control limits are appearing as 0.0 because they are calculated directly from your historical process data. If the Numerator values used for the calculation have all been zero, then the average rate is also zero. Since control limits are based on the average and the variation around it, a zero average with no variation results in zero-value limits. For example, the general formula is:
Limits = Average ± (Multiplier × Standard Deviation)If your average and standard deviation are both zero, the limits will also be zero. You'll need historical data with non-zero numerators to generate meaningful control limits.
A properly set Centerline (Target) is absolutely required for the chart's statistical functions, but an Alt. Target is not. The Centerline is the primary reference used to calculate the control limits and apply the rules that trigger the variation icons. In contrast, the Alt. Target is just an optional, visual reference line. It's helpful for comparing performance against a stretch goal or benchmark, but it does not influence any calculations or the variation icons.
Best regards,