Lesson video

Hi, I'm Mrs. Dennett.

And in today's lesson, I'm going to be finding the predicted number of outcomes.

To start this lesson, let's look at some of the key terms that we'll be using.

Can you match up the pink boxes to the green boxes? Let's have a look.

Outcomes are all the results of an experiment.

So when you flip the coin 10 times, what happened? These are the outcomes.

An experiment is just something we're trying out to see what happens.

For example, it could be flipping a coin 10 times, rolling a dice 60 times, or spinning a spinner.

An event is a specific outcome of an experiment.

So if you flip a coin, you could get the tail, that will be called an event.

If you throw a dice, you could get an even number.

That would be an example of another event.

Now let's look at the predicted number of outcomes.

A box contains these shapes.

Mel is doing an experiment.

She takes a shape out of the box, records it and puts it back in the box.

She does this 100 times.

How many times would you expect her to get a green circle? Well, there are 10 shapes in total, and two green circles.

So the probability of getting a green circle will be two tenths.

This means that for every 10 shapes Mel selects, you will expect two of them to be green circles.

So when she does this 100 times, two tenths of the shapes, should be green circles.

Two tenths of a hundred is 20.

We calculated that Mel would expect to get a green circle 20 times.

Remember that this is only an estimate.

It may not happen, but it is a useful way of predicting what will happen.

So to summarise, we have worked out that to find the predicted number of outcomes, sometimes called the expected frequency, we multiply that probability off the event by the number of trials.

Here is a question for you to try.

Pause the video complete the task and restart when you are finished.

Here are the answers.

We can see that there are two black squares out of a total of 15 shapes.

So the probability of getting a black square is two fifteenths.

Similarly, we can find the probabilities for parts two and three.

For part B, we need to use the probability of getting a black square that we found in part A.

This was two fifteenths, We multiply by 300 to get the predicted number of outcomes, which is 40 black squares.

25% of 300 is 75 black squares, which is a lot more than 40.

So although not impossible, it's very unlikely that you would expect to select that many black squares.

Here's a question for you to try.

Pause the video to complete the task and restart when you are finished.

The probability of getting a head on a fair coin is a half.

So we would expect Mo and Rosie to get heads half of the time.

Half 20 is 10, and half of 100 is 50.

Here's a question for you to try, pause the video to complete the task and restart when you're finished.

Here is the answer, on a fair dice probability of getting a six, is one sixth.

So we multiply the probability one sixth, by the number of trials, 600.

This gives us 100.

So we expect Maisie to get a six, 100 times.

Remember this is only an estimate.

That's all for this lesson.

Remember to take the exit quiz.

Thank you for watching.