This sounds like a similar problem to an exercise in the famous probability textbook by William Feller about estimating the total number of fish in a lake by ca

This sounds like a similar problem to an exercise in the famous probability textbook by William Feller about estimating the total number of fish in a lake by catching N of them and tagging them, and then throwing them back in the lake and coming back later to catch another N fish. You check how many of those fish are tagged and derive your estimate from that using the hypergeometric distribution. See the pages here: https://imgur.com/oRF0OD3 https://imgur.com/oRF0OD3 https://imgur.com/UtCZL5A https://imgur.com/UtCZL5A