For teachers

The game in a probability lesson

See why math teachers love borrowing two rubber pigs to demonstrate risk and chance to their students.

Two rubber pigs beat a bag of dice for teaching chance, because nobody knows the answer in advance. A die has six faces and everyone assumes they are equal. A pig has six landings and no two of them are close.

Players: Two or more
Ages: Seven and up
A game runs: Ten to thirty minutes
First to: 100 points
In print since: 1977

What a class can find out for itself

Give a pair of students one pig and a tally sheet. A hundred rolls takes about ten minutes and produces something no textbook table can: a distribution the class measured rather than believed.

Pool the tallies across the room and the shape steadies. That is the law of large numbers happening in front of them, at a scale small enough to see.

Then the harder question

Once each landing has a measured chance, ask what an average roll is worth and what share of rolls end a turn. Both are arithmetic on numbers they collected. From there, the question of when to stop rolling has an actual answer, and it usually surprises people who have been playing for years.

The published counts below come from a sample of nearly twelve thousand rolls. They are useful for checking class results against, but a class that measures its own numbers learns considerably more than one handed these.

The published counts

What a large sample looks like

Compare a class tally against this. Where they differ is worth discussing: sample size, the surface being rolled on, whether the pigs came from a cup.

Sider (no dot)35%
Sider (dot)30.2%
Razorback22.4%
Trotter8.8%
Snouter3%
Leaning Jowler0.6%

Sheets to hand out

The score sheet prints on plain paper with the scoring chart in the margin, so it works as a tally sheet without any explaining.

Print a sheet

The maths written out

Expected value, chance of busting, and where banking beats rolling, worked through with the numbers rather than asserted.

When to stop rolling