“A person without data is just another person with an opinion” (or, Without data, you’re just another person with an opinion” is a popular phrase of uncertain authorship. “Without data you are just another person with an opinion” was cited in print in 1988. The saying is often credited to American statistician W. Edwards Deming (1900-1993), but the line does not appear in his books.
 
“Without backup data, you are just another person with an opinion” was a popular saying in Total Quality Management (TQM) in the 1990s. “In God we trust. All others must bring data” is another popular saying about data.
 
     
Google Books
Human Factors in Aviation
By Earl L. Wiener and David C. Nagel
San Diego, CA: Academic Press
1988
Pg. ?:
For this reason, airlines must capture and analyze data more effectively to provide factual information to drive training needs (‘Without data you are just another person with an opinion’).
 
Google Books
World Class Production and Inventory Management
By Darryl V. Landvater
New York, NY: Wiley
1993
Pg. 77:
Fred Miller of Industrial Engineering has a saying: ‘Without data you’re just another person with an opinion.’
 
Google Books
Breakthrough Creativity!:
Developing Ideas that Make a Difference
By Marlene Caroselli
White Plains, NY: Quality Resources
1994
Pg. 15:
A popular saying in the world of TQM is, “Without backup data, you are just another person with an opinion.”
 
Google Books
Strategic Management Accounting:
Text and Cases
By Malcolm Smith
Boston, MA: Butterworth-Heinemann
1997
Pg. 3:
To paraphrase W Edwards Deming: ‘In God we Trust, All others bring Data’ and ‘Someone with an Opinion and No Data is just another person with an opinion’.
   
Google Groups: rec.aviation.rotocraft
Newsgroups: rec.aviation.rotorcraft
From: .(JavaScript must be enabled to view this email address)
Date: 1997/11/15
Subject: Fitting Name—Dopey
(...)
We suggest that you take the following saying and hang it on the bathroom wall just over the toilet so you have something to read, instead of the supposed rumors that you’ve obviously gotten from the walls at your local truckstop.  Here it is, write it down: “An engineer without data is just another person with an opinion!”    The reason we have written this paragraph in this manner, is because we really have a hard time respecting you or your opinion, when you’re hiding behind an alias and not only spreading rumors, but probably making them up as well.
   
BMJ (British Medical Journal)
25 June 2003,
“a person with an opinion and no data is just another person with an opinion”
 
18 November 2004, The Daily Times (Farmington, NM), “Parents’ right defined at special ed workshop” by Jim Snyder, pg. A4, col. 4:
“Without data you’re just another person with an opinion.”
(Gary Smethurst, family liaison advocate—ed.)
     
Armchair General and HistoryNet
Crash
03 Jun 05, 10:36
(...)
I have a sign in my office that says “A person without data is just another person with an opinion”.
 
Google Books
Web Based Enterprise Energy and Building Automation Systems
Edited by Barney L. Capehart and Lynne C. Capehart
Lilburn, GA; The Fairmont Press, Inc.
2007
Pg. 8:
A person without data is just another person with an opinion.
 
Amazon.com
1.0 out of 5 stars An Unhappy Reader, August 9, 2009
By statdude “Jim” (CO)
This review is from: The Politically Incorrect Guide to the Great Depression and the New Deal (The Politically Incorrect Guides) (Paperback)
This book was quite a disappointment.
 
I was looking forward to a book that would demonstrate with facts the von Mises point of view on the economics of the Great Depression. What I read was a book that had some good points and a lot of comments that were the authors opinion that he stated without support. Statisticians have an expression, “A PERSON WITHOUT DATA IS JUST ANOTHER PERSON WITH AN OPINION”. This book fits that expression.
 
Google Books
Statistics for Management and Economics
By Gerald Keller
Mason, OH: South-Western Cengage Learning
2012
Pg. 388:
W. Edwards Deming, a famous statistician, said it best: “Without data you’re just another person with an opinion.”
 
Twitter
EdLeader21
‏@EdLeader21
Andreas Schleicher’s great tag line “Without data, you’re just another person with an opinion” #deeperlearning #edleader21
6:23 AM - 3 Apr 13