Every week I have a look at the average age report, use the same filter, timeframe and lookback window. I noticed the data of previous weeks changes, this seems incorrect, as those weeks have past, so the data of these weeks shouldn't change.
For instance this week the average age of last week is 118, but when I looked last Monday it was 105.
Even if items that were on the backlog last week the average of that week shouldn't change today, as the average of the issues last week shouldn't go further than last week.
Am I missing something here?
I was able to find some information on how it's calculated:
The Average Age Gadget displays a bar chart showing the average number of days that issues have been unresolved. For every issue, we:
We then compute the amount of time the issue has been opened up to the end of this period using min(resolutionDate, periodEndDate) – issueCreationDate and increment a count of open issues for that period.
The result is a map of periods to total time that the issues have been opened. We compute the average by dividing the total time by the total number of issues recorded per period.
This gadget does rely on the
org.apache.lucene.search.Collector implementation. It's possible if there were some index inconsistencies that were solved by a later reindex, that this could explain the difference in numbers.
If you want to dig deeper, the code can be found in https://stash.atlassian.com/projects/JIRASERVER/repos/jira/browse/jira-components/jira-plugins/jira-gadgets-plugin/src/main/java/com/atlassian/jira/gadgets/system/AverageAgeChartResource.java#41,48,60,76,121.
I hope this answer is helpful.
@Sanne van Tongelen, I have always found the chart to be difficult to consume but TBH i have not spent a lot of time recently trying to decode the math. I would be interested in your observations week-over-week. Specifically, do you see that week-over-week the the bar changes for several weeks back (not just last week). I don't know what you mean by "total age". My understanding is this chart is trying to illustrate if you are keeping up w/ you backlog or not. If the trend is climbing then you are falling behind if declining you are making positive progress and if level then you are treading water. I haven't monitored the number much.
Thanks for your response.
I understand that it is meant to see if you keep up with your backlog.
We weekly keep track of the average age to see how we are doing over time and motivating the Product owner to keep the average age at a certain level. However we found the data to be inconsistent, at least to what we expect. Maybe we are expecting the wrong thing.
I added the numbers in our external KPI dashboard and in week 35 and 36 I had the numbers: 117 and 118.
However if I have a look at the chart today it has changed to 122 and 121:
In my opinion that wouldn't be possible, as that is changing the past. Today's stories shouldn't change the average of past weeks as the average back then was the average on that point in time.
Hopefully this creates clearance on my issue. :)