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