Watch as we draw the SAME data set three times in a row — first with the y-axis stepping every 1, then every 2, then every 5. The numbers are identical each time, but the chart tells a different story at each scale. Then a fourth chart shows what happens when one bar is much bigger than the others.

Same data, yStep 1

Every square on the y-axis is worth 1. Easy to read off exact values, but the chart climbs all the way up to 12 and looks crowded.

Same data, yStep 2

Every square is worth 2. The chart is half as tall, much cleaner, still easy to read.

Same data, yStep 5

Every square is worth 5. Now we cannot tell 3 from 5 — the two smallest bars look almost the same. We have lost detail.

Big counts, yStep 5

One bar is 30, far bigger than the others. yStep 5 keeps the tall bar on the page and still leaves the small bars readable.

Today we explore: the same data set across four yStep settings — 1, 2, 5 and 10. Before each switch, predict which scale will tell the story best. Then a pupil at the board sets the yStep, and we check together.