This is a review of basic concepts of mean, median, mode, and range. It includes the concept of multiple modes, which is sometimes tested on the ACT.
I find it helpful to let my students know that the mathematical community is divided on precisely what the mode is of the following sets:
{1, 1, 1} (Some say it's 1, some say there is no mode, since no value occurs more frequently than another.)
{1, 2} (Some say it has two modes, and some say there is no mode.)
I use this activity within cooper