CASE 17
Tasker Milward Science
Mod9_1
Probability
Names ……………………………………………………………………………………………………………………………
Spinning coins
Activity 1 Heads and tails
We can use coins to model probability or
chance.
When you spin a coin how likely is it that you will get a long run of heads?
Do you think it is easier or harder to get three heads in a row than to get
ten heads in a row?
Why do you think that?
Let us test out your
ideas.
Spin one coin fifty times and record if it
lands heads (H) or tails (T) in the
Table A.
Table A
Runs of
heads
126
CASE 17
Tasker Milward
Science Mod9_1
Names ……………………………………………………………………………………………………………………………
Activity 2 The frequency of runs
Let us look at runs of heads in your group’s fifty throws (Table
A).
Use a coloured crayon to mark all the runs of two heads, a
different colour to mark runs of three heads, another colour for
four heads etc.
Put the number of each type of run (2s, 3s, 4s etc.) into the
frequency Table B.
1 To the nearest whole number, how many
times did you get one head on its own
compared with runs of two heads?
Table B
Frequency
Runs of:
2 heads
2 To the nearest whole number, how many
times more runs of two heads are there
than runs of three heads?
3 heads
4 heads
5 heads
3 Can you see any pattern in your frequency
table?
6 heads
7 heads
8 heads
Now add your group’s data to the
class results.
Looking at the class results, discuss
these questions in your group:
9 heads
10 heads
11 heads
12 heads
4 Is there a pattern in the runs of heads?
5 To the nearest whole number, how many times more runs of two heads
are there than runs of three heads?
6 Suppose you throw two heads in a row. On the next throw, what do you
think are the chances of getting a head?
7 Does the answer to Question 6 explain your answer to Question 5?
Frequency
CASE 17
Tasker Milward Science
Mod9_1
Names ……………………………………………………………………………………………………………………………
Activity 3 Small samples
What do you notice about the number of heads in a sample of ten compared
with a sample of fifty coin throws?
From Table A, count the number of heads in the first set of ten
throws, then in the second set of ten throws, then in the third set
etc.
Complete Table
C
Table C Number of heads in sets of ten
Did you get exactly five heads in any of the sets
throws
of ten throws?
Set of ten throws
What was the largest number of heads in any
set of throws?
First set of ten throws
Second set of ten throws
What was the smallest number of heads in any
of your sets of throws?
Third set of ten throws
A set of ten throws is a sample of
the possible ratio of heads to
tails.
What are the chances of a head being thrown?
Fourth set of ten throws
Fifth set of ten throws
What are the chances of a tail being thrown?
Why?
How many times do you think you would have to throw a coin to get equal
numbers of heads and tails in the whole sample? Take a guess.
Does a sample of ten throws tell us much about the ratio of heads to tails?
How many sets would you want to look at to give you a big enough sample for
you to look for a pattern, a ratio? Take a guess.
People say that each time a baby is conceived it has an equal
chance of being a girl or a boy.
You could not look at every single birth record in the country to
find the ratio of boy babies to girl babies. It would take you too
long.
Number of heads