Probability Line

Probability is the chance that something will happen. It can be shown on a line:

probability 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:

We can use fractions:

probability line fractions

Or percents:

probability line percents

Or decimals:

probability line decimal

Example: here we show the probability that:

probability line examples

Where would you place names like "fair chance", "remote chance", "possible", "probable" and "improbable"?

Between 0 and 1


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


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!


An Experiment with a Die
An Experiment with Dice