what do you mean by "activity time".
Do you mean "activity work" ?
If so, I don't get the interest as it depends on how you split your activities.

Idea is to have a statistique for every project (close included) with average time to make a activity work per type activity.

Example => My type of activity : make tools, control tools, valided tools

For each Project I have this activity

And I would like to see the average time between "handled date" to "real end date" but per type of activity and per Project, please.

OK I find a solution just when I export an excel sheet on the activity page, I need the colonne "type of project", because i need to make statistic with type of activity and type of project.

Thank you for your help

Bets regards,