[VSA] "Days to completion" chart should not use totals
Problem to solve
The "Days to completion" scatterplot was added to group-level Value Stream Analytics under #12078 (closed). Currently this chart displays the total time spent in the given stage by all items that completed the stage on each date. Using total seems fundamentally flawed.
If multiple items coincidentally exit the given stage on the same date, the value for that date will tend to be much higher than other values. However, that high value does not indicate high or low functioning - in fact it is probably useless information because it cannot be compared to the other data points.
More generally, this chart was originally described as, "Essentially, the added value of all stages in Cycle Analytics for that date." However, time does not equal value. In fact, it is obviously more valuable to deliver the same work in less time. So totals are possibly even counterproductive.
- The "Days to completion" scatterplot should display average time to complete the stage (not total/combined time).
- This should be reflected in the documentation per !43446 (comment 424939811).