Latin square is a NxN square with a number of N different elements which are in N distinct orders for the N rows (also the N columns). For example,
is a Latin square. What can it be used in designing a experiment or user study? For instance, if you have N tasks and you want to have someone to do these tasks and measure their performance. One way to do it is to recruit N participants and each participant corresponds to one distinct arrangement of the N tasks. In this way, there is no bias for each tasks.