Normal Probability Paper

Understanding the layout

This layout places probability percentages along the horizontal axis and leaves the response axis linear and unlabeled. Percentages near the tails spread differently from those near the center. The 50% guide marks the midpoint, while the displayed range runs from 0.1% to 99.9%. Neither 0% nor 100% has a finite normal quantile, so those endpoints are not printed. The reference below explains the underlying normal probability plot method.

Using the sheet

Sort the observations and choose a plotting position convention appropriate to your assignment. Mark the response values on the linear axis, then plot each value at its corresponding probability position. Write down which convention you used so another reader can reproduce the work. The paper is a visual aid for comparing a pattern, not a substitute for checking sample size, measurement problems or the assumptions of a statistical analysis.

Choosing the settings

The paper controls change the available plotting area while preserving the probability mapping. Use landscape orientation when the tail labels need more horizontal room. The percentages identify probabilities, not data values or confidence levels for a particular observation. A labeled center line helps orient the sheet when it is copied or photographed separately from your notes.

A practical example

Open the default sheet and download an SVG. Locate 50% at the center of the probability axis. The guides for 10% and 90% should be equally far from that center, as should 1% and 99%. Use that symmetry as a simple check before entering your own ordered data.

Before you print

The tool does not sort observations, assign plotting positions, fit a distribution or return a statistical test. A roughly straight plot is not by itself a guarantee of normality or of valid conclusions.

Printing and file format help · Check your print scale

Common question

A Printable Paper Lab guide. How these tools and guides are made.