Statistical Symbols and Abbreviations - Study Design and Statistics

AMA Manual of Style - Stacy L. Christiansen, Cheryl Iverson 2020

Statistical Symbols and Abbreviations
Study Design and Statistics

The following may be used without expansion except where noted. For a term expanded at first mention, the abbreviation may be placed in parentheses after the expanded term and the abbreviation used thereafter (see 13.11, Clinical, Technical, and Other Common Terms). Most terms other than mathematical symbols can also be found in 19.5, Glossary of Statistical Terms.

Symbol or abbreviation



absolute value



greater than

greater than or equal to


less than

less than or equal to


hat, used above a parameter to denote an estimate


analysis of variance (expand at first mention)


analysis of covariance (expand at first mention)




alpha, probability of type I error

1 − α

confidence coefficient


beta, probability of type II error or population regression coefficient

1 − β

power of a statistical test


sample regression coefficient


confidence interval

C statistic

concordance statistic (same as C index)

Image (chi-square)

χ2 test or statistic, with 3 df shown as an example


coefficient of variation (s/x̄) × 100 (expand at first mention)


Cohen d




degrees of freedom (v is the international symbol149 and also may be used if familiar to readers)


Mahalanobis distance, distance between the means of 2 groups


delta, change, difference


delta, true sampling error

epsilon, true experimental error




expected value of the variable x


frequency or a function of, usually followed by an expression in parentheses, eg, f(x)


F test, ratio of 2 variances. This test can be represented by Fv1,v2(1 − α), where df = v1, v2 for numerator and denominator, respectively, and (1 − α) = confidence coefficient


likelihood ratio χ2


hazard ratio (expand at first mention)


null hypothesis


alternate hypothesis; specify whether 1- or 2-sided


test for heterogeneity


kappa statistic


lambda, hazard function for interval i; eigenvalue; or estimate of parameter for log-linear models


Wilks lambda


natural logarithm


logarithm to base 10 (log10)


multivariate analysis of variance (expand at first mention)


population mean


size of a subsample


total sample size


(n) factorial


odds ratio (expand at first mention)


statistical probability


bivariable coefficient of determination


multivariable correlation coefficient

r 2

bivariable coefficient of determination

R 2

multivariable coefficient of determination


relative risk (expand at first mention)


rho, population correlation coefficient


sample variance


sigma squared, population variance


sigma, population SD


standard deviation of a sample, can also mean standardized difference


standard error


standard error of the mean


t test; specify α level, df, 1-tailed vs 2-tailed


Kendall tau


Hotelling T2 statistic


Mann-Whitney U (Wilcoxon) statistic


arithmetic mean


z score

Principal Author: Edward H. Livingston, MD


Thanks to the following for reviewing and providing comments to improve the manuscript: Miriam Cintron, JAMA; Trevor Lane, MA, DPhil, Edanz Group, Fukuoka, Japan; Tom Lang, MA, Tom Lang Communications, Kirkland, Washington; and Ana Marušić, MD, PhD, Journal of Global Health and University of Split School of Medicine, Croatia.


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Additional Reading and General References

Elliott AC, Woodward WA. Statistical Analysis Quick Reference Guidebook: With SPSS Examples. Sage Publications; 2007.

Guyatt G, Rennie D, Meade M, Cook D, American Medical Association. Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. 3rd ed. McGraw-Hill Education Medical; 2015.

Livingston EH, Lewis RJ. JAMA Guide to Statistics and methods. McGraw-Hill Education; 2020.

JAMAevidence. Accessed November 9, 2019.

Motulsky H. Intuitive Biostatistics: A Nonmathematical Guide to Statistical Thinking. 3rd ed. Oxford University Press; 2014.

Riegelman RK, Riegelman RK. Studying a Study & Testing a Test: Reading Evidence-Based Health Research. 6th ed. Wolters Kluwer/Lippincott Williams & Wilkins Heath; 2013.

Rothman KJ, Greenland S, Lash TL. Modern Epidemiology. 3rd ed. Wolters Kluwer Health/Lippincott Williams & Wilkins; 2008.