In God we trust. All others must bring data.
Notes from Wikiquote
Frequently attributed to Deming; it appears in The Deming Management Method, by Mary Walton, 1986, p. 96, without any attribution, to Deming or anyone else | Chapter 20: Doing It with Data: "In God we trust. All others must bring data." If there is a credo for statisticians, it is that.