When did E. Hopf say "ergodic theory is statistics and statistics is measure theory"?

Question

In the archived version of Kolmogorov's Foundations of the Theory of Probability, at the very end of the book, p. $84,$ few books have been listed, one being E. Hopf's Ergodentheorie, where it is mentioned

Measure theoretic viewpoints are preferred over topological ones throughout because, as the author says, ergodic theory is statistics and statistics is measure theory.

I have done preliminary googling but so far I didn't come across any helpful site or source that mentions his quote, the time (at least earlier than $1937,$ the publication year of the said book) he asserted that or the context.

So, the question is: when and where did E. Hopf assert the concerned statement?

Answer 1

The blurb shown in the question quotes from a review of Eberhard Hopf's book Ergodentheorie, Berlin: Springer 1937, by Béla Szőkefalvi-Nagy in Acta Scientiarum Mathematicarum (Szeged), Vol. 9, No. 3, 1938-40, pp. 197-198 (volume online). The relevant sentence is on page 197 and reads as follows:

Maßtheoretische Gesichtspunkte nehmen in der ganzen Darstellung den Vorrang vor den topologischen ein, da, wie der Verfasser betont, Ergodentheorie Statistik ist und Statistik Maßtheorie.

The language pretty clearly indicates that the reviewer is quoting Hopf from the book under review, but I do not have access to the book to verify that. I am making this a community wiki answer to allow easy addition of this information at a later stage.