WeBWorK has a Reduced Scoring Period, that is a period before the due date during which all additional work done by the student counts at a reduced rate. This can be used to encourage students do assignments on time with a grace period (the Reduced Scoring Period) during which their work counts at a reduced rate. It can also be used at the end of the semester to encourage students to work on problems thay did not get completely correct. To do that, simply change the due dates of all assignments (e.g. to the day before the final exam thereby reopening the assignments), set the Reduced Scoring Period to a fairly long time (greater than the time between when you reopen the assignments and the new due date), and enable reduced scoring for the assignments.
Here is how the Reduced Scoring Period works. There are two parameters, the reducedScoringPeriod which is the length in minutes and the reducedScoringValue, a number in [0,1] which gives the value of work done in the Reduced Scoring Period. Suppose the reducedScoringPeriod = 60*24*2 (two days) and the reducedScoringValue = .5. On the page listing the problems, the student will see a message like:
This assignment has a Reduced Scoring Period that begins 11/08/2009 at 05:00am EST and ends on the due date, 11/10/2009 at 05:00am EST. During this period all additional work done counts 50% of the original.
If reducedScoringPeriod = 0, no message is displayed. If the reducedScoringPeriod is positive and the reducedScoringValue = 1, a message will be displayed stating that all additional work done counts 100% of the original. This might be a gentle way to introduce students to Reduced Scoring without really penalizing them. They will see all the messages but their work will count 100%.
Before the Reduced Scoring Period everything is exactly like a normal problem. For example if a student does 6 parts of a 10 part question correctly, they see
You received a score of 60% for this attempt. Your overall recorded score is 60%.
During the Reduced Scoring Period the student sees the message
Note: You can earn partial credit on this problem. You are in the Reduced Scoring Period: All additional work done counts 50% of the original.
Suppose during the Reduced Scoring Period they attempt the problem again and get 9 of the 10 parts correct. They see
You received a score of 90% for this attempt. Your overall recorded score is 75%.
Finally if they go back to the problem and get all 10 parts correct they see
You received a score of 100% for this attempt. Your overall recorded score is 80%.
To use Reduced Scoring go to "Course Configuration", click on "PG - Problem Display/Answer Checking" and fill in the values you want for "Length of Reduced Scoring Period in minutes" and "Value of work done in Reduced Scoring Period". Then you have to enable Reduced Scoring for whatever assignments you want to use it for. To do this go to "Hmwk Sets Editor" and edit the set data for the assignments checking the "Enable Reduced Scoring" box (or selecting "Yes" in the "Reduced Scoring Enabled" box if you are editing all set data.
Reduced Scoring only works with the avg problem grader (this is the default grader) or the std problem grader (the all or nothing - no partial credit grader). If you want to use Reduced Scoring with a custom grader, you will have to implement it in the custom grader using the above graders as guides.