# Thread: Creating groups that don't repeat

1. ## Creating groups that don't repeat

If you have a class of 90 students:

Year 1, you want to split them into 2 equal groups
Year 2, 3 equal groups (or near equal)
Year 3, 4 groups
Year 4, 5 groups
Year 5, 6 groups

****The students should not be in the same group as someone they have already been with (as much as possible)

What formula can I use?

2. Originally Posted by Marc
If you have a class of 90 students:

Year 1, you want to split them into 2 equal groups
Year 2, 3 equal groups (or near equal)
Year 3, 4 groups
Year 4, 5 groups
Year 5, 6 groups

****The students should not be in the same group as someone they have already been with (as much as possible)

What formula can I use?
You can't avoid that some students from year 1 will be in the same group again in year 2. For example, the 45 students who were in group A in year 1 must be spread among three groups in year 2. The best you can achieve then is that each group in year 2 has 15 students from group A of year 1 and 15 from group B of year 1.

A reasonable mix can probably be achieved by randomly assigning each student to a new group in each year. For a better mix, consider using quasirandom numbers.