Black and white

Black and white

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This task is about comparing probabilities.
BW-spinner.png
The arrow on this spinner has an equal chance of stopping on black or white when it is spun.

Question

a)  The arrow is spun once. Which of these is most likely?
    • The arrow points to black.

    • The arrow points to white.

    • Each of these two options are equally likely.

    • You cannot tell which option is more likely.

Question

b)  The arrow is spun twice. Which of these is most likely?
    • The arrow points to black both times.

    • The arrow points to white both times.

    • The arrow points to black once, and to white once.

    • Each of these three options are equally likely.

    • You cannot tell which of the three options is more likely.

Question Change answer

c)  The arrow is spun 10 times.
     Drag these statements below into order from the least likely to the most likely.
  • 1 black and 9 white
  • 5 black and 5 white
  • 3 black and 7 white
  • All 10 black
  • 8 black and 2 white
Task administration: 
This task is completed online and has auto marking displayed to students.
Level:
4
Curriculum info: 
Keywords: 
Description of task: 
This task sees what a students understanding of probability is.
Curriculum Links: 
This resource can be used to help to identify students' understanding of ordering probabilities.
Learning Progression Frameworks
This resource can provide evidence of learning associated with within the Mathematics Learning Progressions Frameworks.
Read more about the Learning Progressions Frameworks.
Answers/responses: 
  Y8 (11/2015)
a) C - Each of these two options are equally likely. easy
b) C - The arrow points to black once and white once. moderate
c)
All 5 correct
 
answer-black-white.png
moderate
Based on a sample of 100 Year 8 students
Teaching and learning: 
The key element in this task is recognising which outcomes of a chance event are more probable that others.
Diagnostic and formative information: 
Equiprobabily misconception
b) Students tick "Each of these three options are equally likely."
The student sees events as equally likely, even when the events have different probabilities. This error involves either:
  • ignoring the different probabilities of events; or
  • ignoring that 1 black and 1 white can occur two different ways, and is therefore twice as likely as 2 blacks (which can only occur one way).

See Throwing a coin for a resource that also has this as a common misconception.
 

Next steps: 
Equiprobabily misconception
Get the student to record the results for a game with equal probabilities by making a spinner. Click on Making spinners for instruction on how to make a fair spinner. With a large number of spins, students should observe that 1 black and 1 white is twice as likely as 2 blacks or 2 whites. The results of this could be discussed, and students encouraged to note that black followed by white, and white followed by black both lead to a total of 1 black and 1 white.

Students could also write down the 4 possible options using either:
  B W
B B B B W
W B W W W

For more information click on the Probability concept map