  The apparent clustering in longitude of perihelion $\varpi$ and ascending
node $\Omega$ of extreme trans-Neptunian objects (ETNOs) has been attributed to
the gravitational effects of an unseen 5-10 Earth-mass planet in the outer
solar system. To investigate how selection bias may contribute to this
clustering, we consider 14 ETNOs discovered by the Dark Energy Survey, the
Outer Solar System Origins Survey, and the survey of Sheppard and Trujillo.
Using each survey's published pointing history, depth, and TNO tracking
selections, we calculate the joint probability that these objects are
consistent with an underlying parent population with uniform distributions in
$\varpi$ and $\Omega$. We find that the mean scaled longitude of perihelion and
orbital poles of the detected ETNOs are consistent with a uniform population at
a level between $17\%$ and $94\%$, and thus conclude that this sample provides
no evidence for angular clustering.
