This is a set of dice, some of which are unfair!
I have weighted them so that they are not obviously unfair, but after a few hundred rolls it will become obvious that one number comes up a bit too often.
The filenames indicate which number is more likely.
All dice should weigh the same. The fair die has the same size void at the centre of the die.
Print this will high infill so the die has enough weight. I have tested this model with a 95% infill.
The dice will all look good with whatever infill you use, the difference is in the distribution of mass.
Overview and Background
This thing was designed for an investigation at the end of a statistics unit to get my students to grapple with the idea of sampling variation. This is a tricky concept and can be hard to get to terms with. In this investigation the students needed to decide when they had enough data to be confident about their results.
Usually after 300-400 rolls it is clear that the die is weighted.
Lesson Plan and Activity
Print a enough of dice so that each pair of students will get three dice. Print half fair, half weighted.
Divide up the dice so that each set of three has one fair, one weighted and one other.
Instructions for students
Each set of dice has at least one unfair die.
You need to roll the dice until you are confident that you can identify which dice are fair and which are unfair.
You will present your findings to the class.
The presentation will include:
Graphs of your experiments
Percentages for each die
Your conclusion about your dice
I offered a bribe of chocolate if they were able to correctly identify all three of their dice.
- bar graphs
Print the dice and lable them (A-Z). Record how each die is weighted so you can tell if they have correctly identified the dice. You can also see the location of the hole by holding the die up to a strong light.