Regarding the assumption of full use of the binary space... May I phrase that differently? azAZ and 09azAP both leave big swaths of the space as always-zero or perhaps always-one. Another way to phrase it: you could write out an azAZ string using five-bit characters and have room to spare.

The swaths of emptiness in the range of possible values is why I took an English sample and did my best to encode it the same way as the original was, so that we'd have an apples-to-apples comparison. The English sample had higher entropy than the original--after "accounting for" encoding.

You are right, my method of "accounting for" encoding did nothing for the "serial correlation coefficient" metric. I didn't know what that was until you mentioned it, thanks.

Your actual/expected analysis is a good idea, though it took me a minute to understand what you were doing. I guess: "If these are truly random digits from azAZ, then half of them will be uppercase." Indeed. But... I just read an article[0] which convinced me that I have no idea how "random" works. (Specifically this bit: As an example, the probability of having exactly 100 cars is 0.056 — this perfectly balanced situation will only happen 1 in 18 times.

Cheers.

0: https://www.quantamagazine.org/20150925-solution-the-road-le...