Scatter Plots and Trends

≈ 20 min

A scatter plot shows the relationship between two quantities by plotting a point for each pair of measurements. The pattern of the dots reveals the correlation:

Positive correlation — as one variable goes up, so does the other (dots trend upward).
Negative correlation — as one goes up, the other goes down (dots trend downward).
No correlation — the dots are scattered with no clear direction.

A single point sitting far away from the rest is an outlier — often an error or an unusual case worth investigating.

When there's a clear trend, we can draw a line (or rule) of best fit through the middle of the points and use it to predict values, for example estimating a learner's mark from the hours they studied.

On a scatter plot, as one variable increases the other also increases. This shows…

positive correlation

negative correlation

no correlation

an outlier

A scatter plot has the points $(1,2)$ , $(2,4)$ , $(3,5)$ , $(4,7)$ and $(9,3)$ . Which point is the outlier?

$(2,4)$

$(3,5)$

$(9,3)$

$(4,7)$

A study finds a rule of best fit $m = 10h + 30$ , where $m$ is the test mark (%) and $h$ is hours studied. Predict the mark for a learner who studies 5 hours.

Using the same rule $m = 10h + 30$ , how many hours of study does the line predict for a mark of $60\%$ ?