Scatter Graphs
Plot bivariate data on a scatter graph with correctly labelled axes and appropriate scales; describe the correlation (positive, negative, none) and draw an estimated line of best fit where appropriate
What a learner can do afterwards
- Plot 10 data points on a scatter graph with correct axis labels and a consistent scale
- Draw a line of best fit by eye, ensuring roughly equal numbers of points above and below
- Use the line of best fit to estimate a y-value for a given x-value within the data range
The lesson
A scatter graph shows how two things about the same item are related, like hours of sleep and test scores for a group of students. Each point stands for one item, plotted using its two values as coordinates. Before you plot anything, label both axes clearly and choose a scale where equal gaps mean equal amounts, all the way along.
Say you're comparing hours of sleep with test scores for 10 students. One student slept 5 hours and scored 60. You'd find 5 on the sleep axis, go up until you reach 60 on the score axis, and mark a single point there. Do that for all 10 students and you get 10 points spread across the graph.
Once your points are plotted, you can draw a line of best fit. It's a single straight line drawn through the middle of the points, showing the overall trend rather than joining any two points exactly. Aim for roughly the same number of points above the line as below it.
To estimate a value with your line, find your known value on one axis, trace up or across to the line, then read off the other axis. This only works for values inside the range you actually plotted; going beyond that range is just a guess.
Label your axes with an even scale, draw one straight line of best fit balanced through the points, then use it to estimate values only within your data's range.
Watch it
Where it sits
Learn first
This opens up
Nothing builds on it yet.
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.