  We examine the results of two measurements by the CLAS collaboration, one of
which claimed evidence for a $\Theta^{+}$ pentaquark, whilst the other found no
such evidence. The unique feature of these two experiments was that they were
performed with the same experimental setup. Using a Bayesian analysis we find
that the results of the two experiments are in fact compatible with each other,
but that the first measurement did not contain sufficient information to
determine unambiguously the existence of a $\Theta^{+}$. Further, we suggest a
means by which the existence of a new candidate particle can be tested in a
rigorous manner.
