The preface to Elements of Statistical Learning opens with the popular quote
In God we trust, all others bring data. — William Edwards Deming
The footnote to the quote is better than the quote:
On the Web, this quote has been widely attributed to both Deming and Robert W. Hayden; however Professor Hayden told us that he can claim no credit for this quote, and ironically we could find no “data” confirming that Deming actually said this.
Emphasis added.
The fact that so many people attributed the quote to Deming is evidence that Deming in fact said it. It’s not conclusive: popular attributions can certainly be wrong. But it is evidence.
Another piece of evidence for the authenticity of the quote is the slightly awkward phrasing “all others bring data.” The quote is often stated in the form “all others must bring data.” The latter is better, which lends credibility to the former: a plausible explanation for why the more awkward version survives would be that it is what someone, maybe Deming, actually said.
The inconclusive evidence in support of Deming being the source of the quote is actually representative of the kind of data people are likely to bring someone like Deming.
The original reminds me of a (once?) common sign:
“In God we trust. All others pay cash.”
Billions of people say that God exists. Is that evidence that He does in fact exist? If the government banned attributing this quote to Deming, and the attribution faded away with time, would it mean he is less likely to have said it?
What is the definition of evidence? Is B evidence for E if P(E|A,B)>P(E|A) ?
If a billion people believe something, that is evidence in its favor. Certainly not proof, but evidence.
There are false statements that a billion people believe. And true statements that nobody believes! But in general, belief by a large number of people is a filter that increases the probability of something being true. It’s not the final word on a subject, but all other things being equal, a greater proportion of statements that a billion people believe are true than statements that only a small number of people believe.
What you mean is that the probability of a statement being true increases with the proportion of people who believes it is true? This means a good rule of action is doing what most people believe is the right thing to do. This increases the probability of doing the right thing.
Isn’t there the same issue as to who is the proper originator of the phrase “All models are wrong; some models are useful.” Was it George Box or George Cox?
“The thing about quotes on the internet is that you cannot confirm their validity.” – Abraham Lincoln
I once took a full semester course called “Theories of Evidence” as a philosophy student. It was fascinating to see how just about any intuitive definition of what makes A evidence supporting B is prone to pathological cases.
(It was a fairly technical course, too, in terms of the amount of conditional probability and modal logic used. It counted toward my applied math degree.)
In a previous job, I had great difficulty in persuading my assistant to say “There is no independent evidence” or the like, rather than “There is no evidence …” where a person had given their account of things.
But, then, I also failed to persuade another young lawyer that a run of heads in a fair coin leaves it equally probable that we’ll have another head. Logic and lawyers don’t always go hand in hand.