Normal plot

Command

Statistics Distribution plot Normal plot

Description

The Normal plot is a graphical tool to judge the Normality of the distribution of sample data.

Required input

Select or enter the variable's name in the variable input field. Optionally, you may enter a selection criterion in order to include only a selected subgroup of cases in plot. When you have completed the dialog box, click the OK button to proceed.

Results

The horizontal axis of the Normal plot shows the numerical values of the observations, and the vertical axis gives the relative frequency in terms of the number of standard deviations from the mean.

A straight reference line represents the Normal distribution. If the sample data are near a Normal distribution, the data points will be near this straight line.

Probably a Normal distribution

Probably not a Normal distribution

Literature

• Altman DG (1991) Practical statistics for medical research. London: Chapman and Hall.

See also

• Histogram
• Cumulative frequency distribution
• Dot plot
• Box-and-whisker plot
• Format graph
• Graph legend
• Add graphical objects
• Reference lines