What is the probability that gravitation wave detections were coincidental errors? The reported discovery of gravitational waves has been put in question by the scientific community:
https://www.quantamagazine.org/strange-noise-in-gravitational-wave-data-sparks-debate-20170630/
In any case, the discovery is based on a short segment of two continuous measurements having an approximately matching pattern (see the plot in the link above). My question is if this match could be just a random coincidence.
Consider two people continuously tossing coins in separate rooms. The results are recorded and correlated. At first they are seemingly random, but given time, there is a certain probability that the results would temporarily match. And the longer we observe, the more likely we get similar patterns.
I have observed a real roulette in a casino for the result to be red or black. Just on the second day of my observation the roulette produced 20 reds in a row. Superficially this is highly improbable, but so is the entire reality.
My question is, what is the margin of error in the gravitational waves discovery data from the standpoint of the probabilistic random coincidence that just looks like correlated signals?
 A: According the LIGO publication:

false alarm rate [is] estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than $5.1\sigma$.

With respect to being called into question, as of today (August 2017) there's still no agreement on that.
After the criticism by the Niels Bohr Institute (NBI) group; the answer from a member of the LIGO collaboration; and the reply from by NBI group; this August (2017) members of the LIGO collaboration visited the NBI for two weeks of discussions. It apparently became clear that there remain "in-principle disagreements" between the teams, with the NBI group summarizing their position on Aug 21st:

We believe that LIGO has not yet attained acceptable standards of data cleaning. Since we regard proof of suitable cleaning as a mandatory prerequisite for any meaningful comparison with specific astrophysical models of GW events, we continue to regard LIGO's claims of GW discovery as interesting but premature.

The community appeared to show a mostly skeptical reaction to the original NBI group paper, and it might be heading to obscurity. If so, it'll be hopefully reflecting flaws in the criticism $-$ and not an over-reliance on the authority of the LIGO collaboration. 
