The relative shift expresses the width of the grey region, or shift, , in terms of the number of standard deviations of the measurement data, , and is designated as (DCGLW - LBGR/ ) or . The degree of difficulty in distinguishing the LBGR from the DCGLW depends on the variability of the data as well as the size of the shift. The smaller the relative shift, the larger the number of samples. The number of samples increases rapidly with only small decreases in the value of the relative shift when the value of the relative shift is below one.
See, Chapter 5: Survey Planning and Design and Appendix D: The Planning Phase of the Data Life Cycle on the MARSSIM Manual download page.