The dog ate my homework!A certain teacher, Mr L I Detector, claims he can tell when students are lying about their homework.This is true.Unfortunately, he also accuses some students who are telling the truth.So what are the chances that someone will be wrongly accused?

Form yourself into groups of 4 or 5, and collect:

•a die•some red, blue, green and yellow cubes•a worksheet

Throw the die.II’’m not m not telling telling

the the truth!truth!

I am I am telling telling

the the truth!truth!

= Anythingelse =

Throw the die.

Who needs to throw the die again to find out what Mr D thinks? Who doesn’t?

II’’m not m not telling telling

the the truth!truth!

I am I am telling telling

the the truth!truth!

= Anythingelse =

Throw the die.

Who needs to throw the die again to find out what Mr D thinks? Who doesn’t?If the student was lying, then Mr D knows, so there is no need to throw the die again.

II’’m not m not telling telling

the the truth!truth!

I am I am telling telling

the the truth!truth!

= Anythingelse =

Mr D Mr D accuses accuses

me!me!➔

If the student is not lying, throw the die again.I am I am telling telling

the the truth!truth!

If the student is not lying, throw the die again.

=

ItIt’’s not fair! s not fair! Mr D Mr D

accuses accuses me!me!

I am I am telling telling

the the truth!truth!

➔

If the student is not lying, throw the die again.

Phew! He Phew! He doesndoesn’’t t accuse accuse

me!me!

=

ItIt’’s not fair! s not fair! Mr D Mr D

accuses accuses me!me!

I am I am telling telling

the the truth!truth!

Anythingelse =

➔ ➔

The experiment•Repeat the experiment 36 times.•First throw of die:

•Second throw of die (if needed):

II ’’m not m not telling the telling the

truth!truth!

=

I am telling I am telling the truth!the truth!

Anything else =

=

ItIt’’s not s not fair! Mr D fair! Mr D accuses accuses

me!me!

Anything else =Phew! He Phew! He doesndoesn’’t t

accuse me!accuse me!

➔

The dog ate my homework!

A certain teacher, Mr L I Detector, claims he can tell when students are lying about their homework.

This is true.

Unfortunately, he also accuses some students who are telling the truth.

So what are the chances that someone will be wrongly accused?

So what are the chances that someone will be wrongly accused?

•What does the evidence of the cubes suggest?•Are you surprised by what you see?

So what are the chances that someone will be wrongly accused?

•What does the evidence of the cubes suggest?•Are you surprised by what you see?•Complete the tree diagram and 2-way table for your results, then add your cubes to the collective 2-way table.•Complete the tree diagram and 2-way table for what you would EXPECT to happen.•How do your results compare?•How about the collective results for the whole class?