Probability plots based on Student's t-distribution

• Published in: Acta crystallographica. Section A, Foundations of crystallography Vol. 65; no. 4; pp. 319 - 321
• Main Authors: Hooft, Rob W. W., Straver, Leo H., Spek, Anthony L.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01-07-2009; Wiley Subscription Services, Inc
• Subjects: Mathematical models; Models, Theoretical; Normal Distribution; Probability; probability plot; Statistical Distributions; Student's t-distribution
• ISSN: 0108-7673; 1600-5724; 2053-2733
• DOI: 10.1107/S0108767309009908

The validity of the normal distribution as an error model is commonly tested with a (half) normal probability plot. Real data often contain outliers. The use of t‐distributions in a probability plot to model such data more realistically is described. It is shown how a suitable value of the parameter ν of the t‐distribution can be determined from the data. The results suggest that even data that seem to be modeled well using a normal distribution can be better modeled using a t‐distribution.