@tsteur opened this Issue on November 11th 2015 Member
  1. Avg time spent on a page is calculated by dividing the sum of all time_spent_ref_action divided by the number of visits nb_visits. Not all visits have time_spent_ref_action though. Instead sum_time_spent should be divided by something like nb_hits_with_time_spent.
  2. In tracker we calculate the time_spent_ref_action wrong. It calculates visit_last_action_time - currentTimestamp but visit_last_action_time is updated on any tracking call, meaning also on any hit.

To make it a bit more clear let's say there are the following tracking calls

  • pageview
  • event
  • pageview

The time spent for first pageview is calculated by the time difference between the event and the pageview, not between the two pageviews. This means for many common scenarios where one triggers a pageview and then an event, search, content impression, ... the time spent information is not accurate.

@hpvd commented on November 12th 2015

uuh good find.- that's quite important!

@SR-mkuhn commented on November 13th 2015
@tsteur commented on November 15th 2015 Member

I think the issue I mentioned here has been an issue for a long time and not only since the last update. From which Piwik version did you update? I presume the problem you are describing might be actually a different one

@mattab commented on November 18th 2015 Member

Marking this issue as duplicate of #9199 - which was renamed to include in its scope this bug

Edit: re-opened this issue as it may be easier to fix this one rather than #9199

@SR-mkuhn commented on November 19th 2015

@tsteur : from 2.14.3 to 2.15.0
And this is just one of 800 Sites tracked in one Piwik instance. (it has effect on the other 799 too)

@SR-mkuhn commented on November 19th 2015

Main Question is: which counting is correct?

@tsteur commented on November 22nd 2015 Member

@SR-mkuhn this particular issue has been buggy for quite a while and not only since last update I think.

@tsteur commented on November 22nd 2015 Member

@SR-mkuhn maybe create a new issue for your problem and describe it there

@sebastianpiskorski commented on February 5th 2016 Contributor

I've also encountered this issue recently. And I've found that there is problem with Metric calculation:

Time spent on site is defined as sum_time_spent and calculated as SUM():
https://github.com/piwik/plugin-CustomDimensions/blob/master/Archiver.php#L164

SUM() function in SQL databases omits records containing NULL values. Later average time spend on time is calculated by dividing this sum by number of visits nb_hits ( https://github.com/piwik/piwik/blob/master/plugins/Actions/Columns/Metrics/AverageTimeOnPage.php#L39 ) which is calculated as COUNT(*) ( https://github.com/piwik/piwik/blob/master/plugins/Actions/Archiver.php#L359 ).

The problem is that COUNT(*) counts all rows, even those containing NULL value. So average value isn't average at all. Solution would be use of SUM(COALESCE(sum_time_spent, 0)) which will count NULL values or introducing nb_hits_with_time_spent as COUNT(sum_time_spent), then using it to divide as @tsteur said.

@petecroaker commented on June 6th 2017

I’ve just encountered the same issue. Checking at the Visitor Profile, I can see that if I look at interactions where we have a page with lots of tracking events occurring, the Page View event gets a minimal time whereas the events are given times between each interaction. As such the user could be interacting on a page for say a minute or more, triggering numerous events, but the page dwell time would be still close to zero. Surely this is a major bug. This means that any page which has subsequent events occurring will have a incorrect dwell time.

@mattab commented on June 6th 2017 Member

Would agree this bug is quite major as it is causing the Time on page to be wrong, for any page tracking events.

@hpvd commented on June 6th 2017

it is causing the Time on page to be wrong, for any page tracking events.

Possibly there is a strong relationship to:
we have no "time on url": Piwik handels events as leaving page (at least in visitor log) #11546

@mgloss commented on November 29th 2018

Has it been already solved? We had Piwik 2.something, now we are in upgrade process to matomo 3.7. and I am wondering if it will be correct. I have checked the previous data in database. Zou can easily see, when filter one specific idvisit in piwik_log_link_action_table and you will see, that every event will close the time on pageview. Especially if you are usinng some events like formSeen, bannerImpression etc. you will understand that it is not correct. And also time spent with some events is soo funny. Thank you also for pointing me to some another issue etc.

@tsteur commented on November 29th 2018 Member

As the issue is still open I don't think anything has been solved here yet AFAIK. @mattab that might be indeed quite important to fix the time on page.

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