It is courteous to contribute equally to a group.
Tina is working on a group project that is due on Monday, when she suddenly has to leave but tells the group that she will work on her part later.
Tina wants to visit her family this weekend.
Tina goes over to her parents' but sets aside time to work on the project in their home office.
Tina spends the weekend at her parents' house and doesn't work on the project at all.
Tina's group members are content and Tina gets a B on the project.
Tina's group members are furious, and they contact the teacher who makes Tina re-do the project alone.