Skill: Conduct a simple probability experiment

A probability experiment is a small chance activity that you can repeat. First, list the possible outcomes. Then make a prediction, try the experiment several times, and record what happens.

Use these words:

• Certain: will happen
• Impossible: cannot happen
• Likely: has a good chance of happening
• Unlikely: does not have a good chance of happening
• Equally likely: outcomes have the same chance

Example: Spin a spinner

A spinner has two same-size sections: one red and one blue.

Step 1: List the possible outcomes

The spinner can land on:

• red
• blue

Landing on red and landing on blue are equally likely because the sections are the same size.

It is certain that the spinner will land on red or blue. Landing on green is impossible.

Step 2: Make a prediction

Before spinning, predict what might happen in 10 spins.

A good prediction is:

Red and blue will happen about the same number of times.

Step 3: Spin and record the results

Suppose the results are:

Color	Tally	Total
Red	`
Blue	`

The tally marks help keep track of each spin. A group of five tally marks is shown by four straight marks crossed by a fifth mark.

Step 4: Compare the results with the prediction

Red happened 6 times, and blue happened 4 times. The results are not exactly the same, but they are fairly close.

This does not mean the spinner changed. In a short experiment, equally likely outcomes may not happen the same number of times. If you spin many more times, the totals may become closer together.