Histograms

A teacher returns a test to thirty students. The scores are 62, 71, 68, 73, 55, 90, 64, 70, 72, 69… a wall of numbers. Staring at the list tells you almost nothing. But sort those scores into piles by tens — 50s, 60s, 70s, 80s, 90s — and the shape of the class jumps out at you: where most students clustered, how many struggled, whether anyone aced it. That pile-sorting, drawn as bars, is a histogram.