How to pick random names and make fair teams
Picking names out of a hat works because every slip has an equal chance. Doing it on a computer fairly takes a little care. This guide covers classroom uses, the common shortcuts that are quietly unfair, and how a fair shuffle works.
The short version
- Enter the names, one per line, and remove anyone who is absent.
- Choose the mode: a wheel for one pick at a time, or a team generator to split everyone at once.
- Turn on “remove the winner” if nobody should be picked twice.
- Spin or shuffle, then reset when the round is over.
Skip the arithmetic. The free Random Name Picker Wheel does this for you, shows the formula and the working with your own numbers, and runs in your browser - nothing you type is uploaded. Also useful: Random Team Generator, Classroom Timer.
Classroom uses
- Cold-calling: picking who answers, with no favourites. With removal on, everyone has a turn before anyone repeats.
- Turn order: spin repeatedly with removal on to set the order for presentations.
- Groups: split the class into teams of any size, or pairs for peer work.
- Jobs and prizes: pick the line leader or a raffle winner in front of everyone, so the choice is visibly fair.
Two shortcuts that are quietly unfair
1. Random number modulo n. A computer produces a random whole number in a fixed range, say 0 to 4,294,967,295. Choosing one of 3 names with “number mod 3” gives names 0 and 1 slightly higher odds than name 2, because 4,294,967,296 does not divide evenly by 3. The fair method redraws the rare numbers in the uneven tail, which is called rejection sampling.
2. Sorting by a random number. Shuffling a list by sorting it with a random comparison looks random but is statistically biased, because sorting algorithms never compare every pair equally often.
How a fair shuffle works
The Fisher-Yates shuffle starts at the end of the list and swaps each name with a name chosen at random from the positions up to and including it. Every one of the n! possible orders is equally likely, provided each random choice is itself unbiased. The names are then dealt out like cards, one to each team in turn, which guarantees team sizes never differ by more than one.
Tips for using it with a class
- Pick a name and ask the question second if you want students to stay alert.
- Keep duplicates deliberate: a name entered twice has twice the chance.
- Do not save a class list on a shared computer without deleting it afterwards.
- If teams must be balanced by ability or must keep certain students apart, random splitting is not the right tool.