Scottish Survey of Literacy and Numeracy
Support Materials
Ideas of chance and uncertainty: Third Level
Part 2
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Third Level: Ideas of Chance and Uncertainty
Experience and Outcome:
MNU 3-22a
I can find the probability of a simple event happening and explain why the consequences of the
event, as well as its probability, should be considered when making choices.
Learning Intention(s)
Success Criteria
I will demonstrate that probability can be
expressed in different forms.
I am able to express probability as a fraction,
decimal fraction and percentage.
I will begin to understand the concept of a
“random” outcome.
I am able to carry out experiments involving
“random” outcomes and analyse the results.
Key Vocabulary
Probability – The chance that an event may happen, which can expressed in words and given as
a fraction, decimal fraction or a percentage.
Impossible event – An occurrence, happening or outcome which cannot happen.
Certain – Will definitely happen.
Favourable outcome – A desired happening or occurrence.
Unfavourable outcomes – An undesired happening or occurrence.
Possible outcome – Capable of occurring.
Bias – A tendency towards a particular outcome.
Random event – Something that happens by chance or without bias.
Learning and Teaching Ideas and possible contexts
1.
Probability Game (Fractions, Decimals and Percentages)
This is a game for two players.

Player 1: Select a card.

Player 2: Try to find a card with the same probability.

If you are correct, score a point and cross out the cards. If you are incorrect, Player 1
scores a point.

Take turns to choose cards and continue the game.

The winner is the player with the most points when all the cards are crossed out.
75%
40%
50%
20%
25%
4%
0.6
0.4
0.3

Pupils could then discuss where they have seen different forms of probability being used
e.g. weather reports using percentages.
Learners should understand that probability could be stated as a fraction, decimal fraction and
percentage.
Why would we never see a probability greater than 100%?
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*Reflective Questions :
How well do you believe your students understand the relationship between fractions, decimal
fractions and percentages?
How can you help your students make the connection?
Can your students see the advantages to using probability in different forms?
2. Online Spinner
This online spinner can be used to demonstrate probability as a percentage and can also be
used to investigate “bias”.
http://illuminations.nctm.org/ActivityDetail.aspx?ID=79
The students are able to create a spinner of their choice. They can add or delete sectors,
change their sizes and colours.
Tell the students to make sure the number of spins is 1, and have them click the Spin button.


How does the experimental probability compare to the theoretical probability?
Click the Spin button a few more times. What happens?
Now have the students change the number of spins to 100, and click the Spin button.



How do the experimental and theoretical probabilities now compare?
Hit the Spin button a few more times. What happens?
What would they expect to happen if they hit the button many times?
Finally, instruct students to increase the number of spins to a very large number (the
maximum allowed is 99,999).



Hit the Spin button one or more times?
Now compare the theoretical and experimental probabilities. What do they notice?
Was their prediction correct?
3. Last One Standing Activity
This is an activity which investigates the idea of a “random” outcome by analysing coin flipping
on a large scale.
Imagine a school assembly with 250 students. Everyone stands up and flips a coin. People
with tails sit down. People with heads flip again.
Ask the students if they think anyone will get 6 heads in a row?
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How many heads in a row do they expect the last student standing to have flipped?
Can they explain their reasoning?
Use the animation in the link below or carry out a practical experiment.
http://nrich.maths.org/7220
Now that they have had the chance to explore, do their answers and reasoning to the
questions above change at all?
What is the probability of flipping ten heads in a row?
How many people would you need to have in a school assembly for you to expect there to be
someone still standing after ten flips?
*Reflective Questions
What strategies could you use to extend your students understanding of random events?
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