To be honest, it sounds like you're pushing uphill a bit trying to do this with a forum activity, for the following reasons:
- YES, you can allow multiple posts,
- YES, you can use a summation of marks to display in the Gradebook,
- YES, you can set each post to be worth a maximum of 50 points,
- BUT then you start to hit up against the problem of the summation of marks blowing out the total to more than the maximum individual mark (and to be honest I'm struggling to see how anyone could use the summation of marks without this happening).
Without doing some tweaking you can't set the max mark in the activity itself to be more than 100, so maybe try the following:
- Set the 'grade' setting in the forum to 75
- Set the 'aggregate type' to 'sum of ratings'
- Mark each post out of 25
- Bingo - you've got a summed total which truncates at 75
- In the Gradebook, use a multiplier of 2 for that gradebook item (assuming you are using Moodle v1.9.x) which will then translate it to 150.
Clunky, but it should work I think...
Note that this won't 'guarantee' that students will make three posts, if you want to do that then you might be better off considering a Database
activity, where you can set more things like that than in a forum.
Hope this helps,
Mark DrechslerNetSpot Pty LtdAustralian Moodle Partner