Back to
GCSE Revision Guide homepage
Relative
Frequency
This page provides a simple example
to illustrate the ideas behind relative frequency.
A
Biased Coin
Suppose you have a coin which you
know is biased towards Heads - this means the Heads has a greater chance of occurring.
However, you do now know what the
probability of a HEAD occurring actually is.
Suppose you tossed the coin lots of
times and go the following data
|
Number of tosses |
10 |
20 |
30 |
40 |
50 |
|
Number of heads |
7 |
15 |
19 |
28 |
34 |
So, to tabulate this we can extend
the table above:
|
Number of tosses |
|
|
|
|
|
60 |
|
Number of heads |
|
|
|
|
|
|
|
Relative Frequency |
|
|
|
|
|
|
As you can see, the probability seems
to be around approaching a value of about 0.68 (to two decimal places).
A good estimate for 
To
improve this estimate we would keep on increasing the total number of tosses.
We
can draw a graph to show how our estimates appear to be approaching 0.68
Deductions
from this and possible questions
·
P(heads)=0.68
THEREFORE P(tails)=0.32
·
If we tossed the
coin 350 times (for example) we would expect 
·
If we tossed the coin 3 times –
we could find the probability of getting THREE HEADS
|
Head |
and |
Head |
and |
Head |
Equals |
Answer |
|
|
|
|
|
|
|
|
