# Teaching about variables with playing cards

Here’s a quick and easy game you can use if you ever need to explain some basic methods concepts like variables or organizing data. It requires only a deck of playing cards (more for large classes) and can work for classes of any size.

Put students into small groups of 3-4 and deal the group a hand of around 10-12 cards.  Then give them five minutes to make as many groupings of cards as possible, with only these rules:

1. They must divide the cards into at least two groups.
2. Each grouping must contain at least two cards.
3. They must be able to name the grouping

I show them an example:  They can organize the cards by Color (3), with two groups, one red, and one black (1), and presumably with 10-12 cards they have at least one of each color (although if they did not, ‘color’ would not be a viable grouping).

Additional rules: They have to write down on paper each of their named groupings–if it is not written down, it cannot count.  The team with them highest number of valid groupings wins (extra credit, a token, or some other prize). Set a timer for 5 minutes and let them get started.

Once time is up, check each team’s groupings. If you have more than 4-5 groups, have groups check each other’s work, and then use one or two as an example for the class.  Clever teams will note that they can make groupings of ‘less than or greater than 2’, ‘less than or greater than 3’ and so on up.

In the debrief, you can note how this gives us insight into variables, and how a single set of subjects (the cards) have multiple characteristics that vary (color, number, suit), and that those characteristics can be organized in a multitude of ways.  It’s a useful exercise to kick off a lesson on measurement, on how theoretical possibilities of variation do not necessarily appear in the actual data, and even on populations and samples (as the cards each group gets are randomly distributed from the deck).  I’ve also found that students tend to organize the cards into only dichotomous categories, which allows for a discussion on categorization and nuance in research methods.