Paired (McNemar) exact binomial, two-sided, alpha = 0.05

 discordant  net needed  as queries   note
          2          --          --   no net difference can clear alpha
          4          --          --   no net difference can clear alpha
          6           6           6   so few flips that only a near-total split counts
          8           8           8   
         10           8           8   
         12           8           8   
         15           9           9   
         20          10          10   
         25          11          11   
         30          12          12   
         40          14          14   
         50          16          16   

`discordant` = queries where the two arms DISAGREE. Queries both arms
get right, or both get wrong, carry no information in a paired test.

⚠ The floor is a function of the FLIPS, not of the set size. A '±2 on 50'
rule of thumb is only right when about 5 queries flipped; at 20 flips it
is far too loose, and at 4 flips it is too strict.
