We discuss observations of the magnetic field , column density , and turbulence in the Cold Neutral Medium ( CNM ) .
The observed quantities are only indirectly related to the intrinsic astronomical ones .
We relate the observed and intrinsic quantities by relating their univariate and bivariate probability distribution functions ( pdfs ) .
We find that observations of the line-of-sight component of magnetic field do not constrain the pdf of the total field B _ { tot } very well , but do constrain the median value of B _ { tot } .

In the CNM , we find a well-defined median magnetic field 6.0 \pm 1.8 \mu G. The CNM magnetic field dominates thermal motions .
Turbulence and magnetism are in approximate equipartition .
We find the probability distribution of column density N _ { \perp } ( HI ) in the sheets closely follows N _ { \perp } ( HI ) ^ { -1 } over a range of two orders of magnitude , 0.026 \lesssim N _ { \perp } ( HI ) \lesssim 2.6 \times 10 ^ { 20 } cm ^ { -2 } .
The bivariate distributions are not well enough determined to constrain structural models of CNM sheets .