Histogram shapes poster

A histogram shows how a measurement is spread: where most values sit, how wide the spread is and whether it fits the tolerance. Its shape is a clue to the process behind it. Two peaks usually mean two processes mixed; a cliff edge often means parts were sorted or readings adjusted; a comb points at the gauge or the class width. This poster draws seven common shapes with what each usually means, and a reminder to draw the limits.

Download the poster

The PNG is free to download now. The print-ready vector PDFs open after a short form, once.

Download PNG (300 dpi)2550 x 3300 px, prints at 8.5 x 11 in · 428 KB · no form

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Histogram shapes poster — 24 x 36 in18 x 24 inA2A3LetterA4PNG 300 dpi

The words on the poster

What the histogram shape tells you

Match the shape first. Then read the numbers.

Bell Most values in the middle. Usual for a stable process.
Skewed Long tail on one side. Often a natural limit, like zero.
Two peaks Two processes mixed: machines, shifts or lots. Split the data.
Plateau Several centres mixed, or the process drifts.
Cliff edge Cut off at a limit: parts sorted out, or readings adjusted.
Island A few values far off: another lot, a gauge error, a one-off.
Comb Bars go high, low, high: gauge resolution or class width.
Draw the limits Is the spread inside the tolerance, and centred?

Shapes after Hitoshi Kume and Kaoru Ishikawa. A shape is a clue, not a proof.

On the floor

How to use it

Putting the Histogram shapes poster to work

1
Hang it where histograms and capability studies are reviewed.
2
When a histogram is drawn, match its shape to a card before reading the numbers.
3
Two peaks or a plateau: split the data by machine, shift or lot and draw it again.
4
Pair it with the free histogram template and Cpk study sheet.

Where the poster goes and how to teach with it, in the order to try them.

Which size to print

24 x 36 in or A2: a main wall or team board, read from a few metres away.
18 x 24 in or A3: a station or notice board. The A3 file also fits 11 x 17 in paper.
Letter or A4: a clipboard, binder or handout, on any office printer.

Every PDF is vector, so it stays sharp at full size. Nothing runs to the edge of the page, so no bleed is needed.