Next, we calculate the chance that two de novo events match at any one of “C” eCNVRs in probands, using methods from the classic “birthday problem” which assess the likelihood of seeing at least one pair of matching birthdays among a given number of people. Our interest was in seeing >2 matches (m) in probands under the null hypothesis of no association with ASD. This calculation is performed empirically by distributing “d” events at random among “C” eCNVRs and then counting the maximum number of CNVs falling in the same location. Repeating this experiment many times, we obtained an estimate of the probability of finding “≥m” counts for ≥1 eCNVR under the null hypothesis.
