Scatter Plots for Kids: Do Taller People Have Bigger Hands?

Bar graphs compare groups. A scatter plot shows whether two measurements go together. It’s a short step from there to thinking like a data scientist.

The question

“Do taller people have bigger hands?” Most students guess yes. Now, can they show it?

The activity

You need: a tape measure, a ruler, squared paper, pencils and a large class graph.

Each student measures their height (without shoes, to the nearest centimetre) and their hand span (thumb tip to little finger tip, fingers spread, to the nearest half centimetre).
Record each student’s pair of numbers.
Draw axes: height across the bottom, hand span up the side. Pick scales that fit the data.
Plot one point per person, at the place where their height and hand span meet.

Read the pattern

Step back. Do the points drift upward from left to right? That’s a positive relationship: as height goes up, hand span tends to go up.

Draw a trend line by eye: a straight line with about half the points above and half below. Don’t join the dots.

Talk about it

Is the relationship strong? How tightly do the points follow the line?
Is there an outlier, a point far from the others? What might explain it? A measurement mistake? A real exception?
Can you use the line to predict the hand span of someone 140 cm tall?

Careful with conclusions

A pattern says taller people tend to have bigger hands, not that every one does. And finding a relationship doesn’t show that one thing causes the other. Here, bigger bodies grow bigger hands, but in other data sets, two things can go together without one causing the other.

Compare graph types

Bar graph: compare amounts in categories (favourite fruit).
Line graph: change over time (temperature through a day).
Scatter plot: the relationship between two measurements.

See our guide to choosing the right graph.

The full lesson is Do taller people have bigger hands? from Data Detectives. Make graphs with our free graph maker. Sign up for three lessons free.