5.02 Independent and dependent events

When we look at the chance of something happening, there are ways in which the chance, or probability could be affected by what has already happened.

Independent events

An independent event means that the chances of that event happening are not changed by what happened before. For example, when we flip a coin, there is always a $\frac{1}{2}$12​ chance that it will land on heads. It doesn't matter whether you tossed a head or tail before. 

To see how this works, let's work through an example where you have four different colored lunchboxes and look at the chance of a particular color being chosen each day.

 

Dependent events

A dependent event means that the chance of that event changes depending on what happened before. For example, let's say you have a lucky dip full of all different prizes. If you pull a toy car out, could someone else choose that same prize? 

Let's look at your lunchbox colors again and see how the chance of picking a particular color changes when you don't bring them home at the end of the day. 

 

Worked examples

Question 1

Question 2

Question 3