Use a Probability Scale to Show Probability

What is the chance the sun will rise tomorrow?

How likely is it that you'll get tails when you flip a fair coin?

How likely is it that a die will land on 7?

 

 

Did you notice that some scenarios are much more likely to happen, while some might be absolutely certain and others impossible?

 

The sun will 100% rise tomorrow.

When something is certain to happen, it has a probability of 1.

(Makes sense as 100% is 1 when converted from percentages!)

 

 

There are two possible outcomes on a coin (heads and tails) - so the probability of getting tails is 1/2.

If something is just as likely to happen as not (even chance), it has a probability of ½ that it will happen.

 

There is no 7 on a die so there is 0 chance that we will get a 7 when we roll it.

If something is impossible, it has a probability of 0 that it will happen.

 

 

Probability therefore can be only numbers between 0 and 1 - you can't get any less of a chance than impossible and any more of a chance than certain!

 

We often visualise it using a probability scale:

 

 

Let's have a go at some questions!