Chapter 7.5 Statistical fluctuations

Mathematical, physical and chemical tables

First Online Edition (2006)

Part 7. Measurement of intensities

  1. A. J. C. Wilson

Published Online: 1 JAN 2006

DOI: 10.1107/97809553602060000608

International Tables for Crystallography

International Tables for Crystallography

How to Cite

Wilson, A. J. C. 2006. Statistical fluctuations. International Tables for Crystallography. C:7:7.5:666–676.

Author Information

  1. St John’s College, Cambridge CB2 1TP, England

Publication History

  1. Published Online: 1 JAN 2006



Chapter 7.5 discusses the effects of statistical fluctuation on the measurement of diffracted intensities. Fixed‐time counting and fixed‐count timing are compared. Complicating factors, such as detector dead time and source fluctuations are analyzed. The problem of measured‐as‐negative intensities is discussed, and strategies for optimization of counting time are analyzed.


  • counting modes;
  • dead‐time;
  • fixed‐count timing;
  • fixed‐time counting;
  • measured‐as‐negative intensities;
  • measurement optimization