IA idea · Games & puzzles

What are the chances of rolling a Yahtzee in one turn?

AA SLAA HLAI SLAI HL Solid Also in: Probability, Networks & graphs

Research question

With the best re-roll strategy, what is the probability of getting five of a kind within three rolls, and how does it compare with simulation and my own games?

Adapt it: change the place, the data or the comparison until the question is yours.

Why it makes a good exploration

The answer (about 4.6%) is not obvious because you keep dice between rolls. Modelling the turn as a chain of states (number of matching dice) is a neat, self-contained probability problem.

The mathematics you'll need

  • Binomial probabilities
  • States and transition probabilities (a Markov chain)
  • Matrix multiplication or tree diagrams
  • Simulation and experimental verification

Course labels show where a technique sits; using maths from outside your course is fine if you explain it clearly and say it is new to you.

Where the data comes from

Play 100+ turns aiming for five of a kind and record results; simulate many more.

Cite every source in a footnote where you use it and in your bibliography. Check the licence of any dataset you download.

A possible outline

  1. Define the states and strategy.
  2. Compute transition probabilities.
  3. Combine three rolls to get the answer.
  4. Compare with simulation and play.
  5. Reflect on strategy choices and extensions.

Pitfalls that cost marks

  • Ignoring that the most common value may change between rolls.
  • Too few experimental turns.
  • Unclear strategy.

Showing personal engagement

  • Play with family and record the results.
  • Compute probabilities for other scoring categories.
  • Decide when to give up on Yahtzee using expected points.

See Criterion C: personal engagement for what examiners look for.

Taking it further

Find the expected score of a turn aimed at a large straight and compare strategies.

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