Normal quantile plot

Definition taught in Descriptive statistics, part of Data analysis

Normal quantile plot

Normal quantile plots of serum creatinine (left) and its reciprocal (right). From Descriptive statistics.

Type	Definition
Taught in	Descriptive statistics
Part	Data analysis

A normal quantile plot, or Q–Q plot, plots the sorted data against the quantiles of the standard normal distribution at the same fractions. If the data come from a normal distribution, the points lie close to a straight line, whose intercept and slope estimate the mean and standard deviation.

Figures

Residual checks for the final birth-weight model. Left: residuals against fitted values, a patternless band. Right: a normal quantile plot of the residuals, close to the line. From Linear model examples.

Used in

• Taught in Descriptive statistics, where the derivation and examples are.
• Also used in Analysis of variance examples · Regression examples · Linear model examples
• All 2 questions on Descriptive statistics

See also

Normal distribution · Sample quantile · Interquartile range · Sample variance and standard deviation · Five-number summary and boxplot

Glossary and index