Upper Control Limit and Lower Control Limit for statistical control analysis

[DannyV]

Hi team, I have a manufacturing process where we calculate the number of days elapsed between date A and date B.

With this information we have the average number of days but I would like to understand if it is in statistical control. To calculate this, we take the average number of days and add 3 standard deviations for the upper control limit (UCL) and subtract 3 deviations for the lower control limit (LCL).

This line should be static for the entire selected date range. Could someone guide me on how to perform the calculation within the calculated field?

To select the start and end dates I have two parameters that I use in order to filter the date ranges.

I’ve been trying with this formula avg({Days}) + (3 * stdevp({Days})) but the limits don’t remain static for the entire time period.

The chart would look something like this:

[duncan]

Hello @DannyV !

I would try this calc instead:
avgOver(sum(Days), []) + (3 * stdevpOver(sum(Days), []))

Let me know if this works!

[DannyV]

Hi @duncan, thanks for the help. You were close, but at least you gave me a starting point.

I’ll leave here the formula I used in case it’s useful to someone:
avgOver({Days}, [], PRE_AGG) + (3 * stdevpOver({Days}, [], PRE_AGG))