Question Video: Using Straight Lines to Model Relationships between Two Quantitative Variables Mathematics • 8th Grade

What type of correlation does this graph show?

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Video Transcript

What type of correlation does this graph show?

The graph shown in the figure is a scatter plot or scatter diagram. These can be used when we have two sets of data related to individuals or events. And we call this bivariant data. We use one set of data for the 𝑥-coordinates and the other for the 𝑦-coordinates and then plot all the data as points on the scatter plot. Our scatter plot will show one of three types of correlation.

Firstly, we have positive correlation. This is when all the points generally slope from the bottom left to the top right of the scatter plot. In this case, as the value of 𝑥 increases, generally, the value of 𝑦 increases. If the correlation is negative, the points will generally slope from the top left to the bottom right of our scatter plot. In this case, as the value of 𝑥 increases, the value of 𝑦 decreases and vice versa. Finally, we have no or zero correlation, as in this graph. There is no obvious pattern between the 𝑥-values and 𝑦-values as can be shown by the two points circled.

The two points have the lowest 𝑦-values on the scatter plot. One of the points has an 𝑥-value between one and two, whereas the other point has an 𝑥-value greater than six. These are the extreme of the 𝑥-values on the scatter plot. This highlights that even when the 𝑦-values are the same, the 𝑥-values vary. We can therefore conclude there is no correlation.

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