From Diversifying Economic Quality: A Wiki for Instructors and Departments
"The collaborative learning lab is where students, usually working in groups of three or four, take a series of short, written quizzes (called unit tests) that correspond to teach of six units in the course. When the class has completed the material in a particular unit students are urged to attempt one of these unit tests, which are taken outside of class at pre-arranged times. A unit test usually consists of about three or four questions or problems and takes approximately 20-30 minutes to complete...(Moore 321)".
Once students arrived at Moore's CLL, a specifically trained CLL tutor (typically a junior or senior economics student) would distribute the tests. Then once each group had time to discuss the questions and determine their answers, the tutor would designate which student in the group would present which question through a process of randomization.
Moore used a process developed by Robin L. Bartlett "to overcome the free-rider problem in group work" with the use of a deck of cards. The tutor would distribute one card to each student for each question, and whichever student received the card with the highest value would be assigned to present that specific question. The students would then proceed to present their answers, and if each member of the group presented their answer to the tutors liking, each member of the group would pass. If not, an incomplete would be recorded for each student, and the group would be advised to take a similar test in the near future.
For the CLL, there was no such thing as failing a test. Any number of attempts was allowed for the unit tests and credit was provided once the test was passed regardless of the number of attempts.