Statistical measurements of dispersion measure fluctuations of FRBs
  Extragalactic Fast Radio Bursts (FRBs) have large dispersion measures (DMs)
and are unique probes of intergalactic electron density fluctuations. By using
the recently released First CHIME/FRB Catalog, we reexamined the structure
function (SF) of DM fluctuations. It shows a large DM fluctuation similar to
that previously reported in Xu & Zhang (2020), but no clear correlation hinting
towards large scale turbulence is reproduced with this larger sample. To
suppress the distortion effect from FRB distances and their host DMs, we focus
on a subset of CHIME catalog with DM $<500$ pc cm$^{-3}$. A trend of
non-constant SF and non-zero correlation function (CF) at angular separations
$\theta$ less than $10^\circ$ is seen, but with large statistical
uncertainties. The difference found between SF and that derived from CF at
$\theta \lesssim 10^\circ$ can be ascribed to the large statistical
uncertainties or the density inhomogeneities on scales on the order of $100$
Mpc. The possible correlation of electron density fluctuations and
inhomogeneities of density distribution should be tested when several thousands
of FRBs are available.
