Dictionary.com
definitions

personal equation

noun
  1. the tendency to personal bias that accounts for variation in interpretation or approach and for which allowance must be made.

Origin of personal equation

First recorded in 1835–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for personal equation

personal equation

noun
  1. the variation or error in observation or judgment caused by individual characteristics
  2. the allowance made for such variation
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
personal equation in Medicine

personal equation

n.
  1. A constant but slight error in judgment, perceptual response, or action that is specific to an individual and is so constant that it is usually possible to allow for it when assessing that person's statements or conclusions, thus arriving at approximate exactness.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.