`kstwobign`  == `ks_two_big_n` == kolmogorov-smirnov for two sample test with a large number of observations
**very** informative
(IIRC  it's the distribution of the max of a Brownian Bridge, or maybe that's the smirnov one :)     `maxbb` distribution.

I never know which is kolmogorov and which is smirnov.