Crossword Puzzle

[LetYouDown]

Siegmund is obviously correct, but to answer your question...if you're truly filling in random letters, your figure is correct. At least in spirit. It does make the assumption that the letters in the puzzle are also randomly distributed and not biased with linguistic trends (such as E being much more common than X).

Actually, no assumption about the distribution of the letters is needed (besides that they are A-Z and not some specialties). Filling truly random letters guarantees that the events of correctness of a particular letter are independent and each has a probability of (1/26) of being correct.