Lesson video

Hello, my name is Mr. Clasper and today we are going to be plotting a scatter graph and describing correlation.

Let's begin with this example.

We're going to plot the information from the table onto our scatter graph.

Our scatter graph compares the time spent revising, with the score of a maths test.

If we look at the first column from the table, we can see that one student revised for two hours and achieved a score of 30.

So on my graph, I'm going to find two hours on my x-axis.

And I'm going to find 30 on my y-axis.

And then I'm going to plot a point where the two lines intersect.

So this point represents the student who revised for two hours with a score of 30.

The next student revised for three hours and achieved a score of 34.

So I'm going to find three hours on my x-axis.

And I'm going to find 34 on my y-axis and plot a point once again.

Our next student revised for five hours, and scored 48.

So I'm going to find five on the x-axis 48 on the y-axis, and plot a point.

This student revised for half an hour or 0.

5 hours and achieved a score of 18.

So I'm going to find 0.

5 on the x-axis, and 18 on the y-axis, and plot a point process for the remaining three columns.

From this data, we can see that as the amount of time spent revising increases, the score on the maths test also increases.

Here's a question for you to try.

Pause the video to complete your task and click resume once you're finished.

And here is your solution for one A.

So remember you're plotting 15 along the x-axis, and 480, then 20 and 335, and so forth.

And you should end up with the points which are displayed on the graph.

Here is part B.

Pause the video to complete your task and click resume once you're finished.

And here is your solution for one B.

So looking at the information that we have on the scatter graph, as the distance from London increases, the sale price decreases and we can see this from the pattern displayed.

Now that we can plot a scatter graph, it's also important that we can describe a correlation, which a scatter graph may show.

A correlation is essentially a pattern revealed by the data.

In this example, we can see that as one variable increases, the other variable also increases.

Or as the time spent revising increases, the score of the math test also increases.

We call this a positive correlation.

In this scatter graph, we've compared shoe size to the score of the mathematics test.

As there is no relationship between these two variables, we say that there is no correlation.

In this scatter graph, we've compared the time spent watching TV with the time spent revising.

We can see that as one variable increases, the other variable decreases.

So as the time spent revising increases, the time spent watching TV decreases.

Or, as the time spent watching TV increases, the time spent revising, decreases.

We call this a negative correlation.

Here's a question for you to try.

Pause the video to complete your task and click resume once you're finished.

And here are your solutions for question two.

So the first example shows that as one variable increases, the other decreases therefore, this is a negative correlation.

The graph at the top right shows that as one variable increases, the other also increases.

So this is a positive correlation and the graph at the bottom shows no correlation at all.

Here's another question for you to try.

Pause the video to complete your task, and click resume once you're finished.

And here are your solutions.

So again, remember that a positive correlation is where both variables increase.

And negative correlation is where one variable increases as the other decreases.

And no correlation means that we have no pattern in our data.

And that brings us to the end of our lesson.

So we've been plotting scatter graphs and discussing correlation.

Why not give the exit quiz a go to show off your skills.

I'll hopefully see you soon.