Twenty Guesses: Information Theory

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This activity introduces the idea that computer scientists measure information by how "surprising" a message is. Learners play the game "20 Questions" and use the number of questions asked as a measure of the value of "information" in the answer. While this is not an intuitive idea, an image of a "decision tree" for guessing a number between 0 and 7 illustrates the relationship between the answers to the questions (yes=1 and no=0), and the answer (so if the answer is 3, then three questions whose answers are no, yes, yes yields 011, which is 3 in binary.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
30 to 45 minutes

Estimated Materials Cost:
free per student

Age Range:
Ages 8 - 14

Resource Types:
Activity, Game, Lesson/Lesson Plan

English, French, Greek, Hungarian, Italian, Polish, Portuguese, Russian, Turkish

Materials List (per student)

  • Worksheet Activity: Decision trees (page 40, optional extension)


  • Engineering and Technology
    • Computing
      • Computer Science
      • Information Systems
    • Engineering
      • Computer Engineering
  • Mathematics
    • Algebra
      • Patterns
    • Data Analysis and Probability
      • Probability
    • Number and Operations

Informal Categories

  • Computers
  • Games


Learning styles supported:

  • Involves hands-on or lab activities