Let’s Crack Zodiac – Episode 2 – Bigrams

2 Responses

1. 

   Nick Pelling · May 17, 2020 at 20:45:46 · →

   Nice video, Dave. 🙂

   What are the bigram “scores” for the top half / bottom half vs their respective random shuffle average?

   As I recall, there are a fair few recurring bigrams that appear in one half but not in the other half at all.

2. 

   admin · May 18, 2020 at 01:04:42 · →

   Hi Nick,

   Thanks!

   I have some details of the top vs bottom bigram bias here:

   http://zodiackillerciphers.com/wiki/index.php?title=Encyclopedia_of_observations#Top_half_.2F_bottom_half_bias

   I measured the bias based on the spread between the top and bottom halves. “In 1,000,000 shuffles, only 2.4% of them had halves with a repeated bigram discrepancy as large as the one observed in the 340 (i.e., a difference of at least 8 repeated bigrams between the halves).”

   As for the raw average per half, I would imagine they’d be half of the shuffle average for the whole cipher. Overall shuffle average was 20 so I’d guess each half would average around 10. Yet Z340 has 9 repeats in the top and only 1 in the bottom.