Step 8 Objective

Find an estimate of the frequency for up to two events.

Examples of what pupils should know and be able to do

In the population as a whole Pr(red hair in males) = 0.2 and Pr(red hair in females) = 0.24.

Given a school has 600 boys and 500 girls find an estimate for the number of red-haired pupils.

Probing questions

How can you work out the frequency for one of the events; for both events?

How do you combine the two frequencies?

What if pupils find this a barrier?

Ask pupils to explain the problem in terms of each event separately and then discuss how they can work out the frquencies before combining them.