Probability Line
Probability is the chance that something will happen. It can be shown on a line:
The probability of an event occurring is somewhere between impossible and certain.
As well as words, we can use numbers to show the probability of something happening:
- Impossible is zero
- Certain is one
We can use fractions:
Or percents:
Or decimals:
Example: here we show the probability that:
- a) The sun will rise tomorrow
- b) I will not have to learn mathematics at school
- c) If I flip a coin it will land heads up
- d) Choosing a red ball from a bag with 1 red ball and 3 green balls
Where would you place names like "fair chance", "remote chance", "possible", "probable" and "improbable"?
Between 0 and 1
- The probability of an event will not be less
than 0.
This is because 0 is impossible (sure that something will not happen). - The probability of an event will not be more
than 1.
This is because 1 is certain that something will happen.
Names
People use many names when talking about probability! Such as odds, chance and so on.
Example: 50/50 chance
means exactly 50% chance, which is also 0.5 or ½
Notation
In mathematics we use the letter P to mean "probability of", like this:
Example: "the probability of choosing an ace is 1 in 13" is written:
P(ace) = 113
It sure saves a lot of writing!