The rural Quinte, Kingston, Rideau DHC had the highest pyloromyotomy rate, and it is unlikely that this highest observed rate is a result of random chance or an outlier based on the size of the child population and the number of pyloromyotomies performed in this DHC. On the other hand, it is possible that because of the small population and low number of pyloromyotomies performed in the more rural DHC of Grey, Bruce, Huron, Perth (the DHC with the lowest pyloromyotomy rate), when compared with the total, its rate could be unstable or unreliable, meaning it could potentially make this DHC a statistical outlier. However, when both these DHCs were removed from the analysis (the lowest rate of 0.95 per 1000 in the Grey, Bruce, Huron, Perth DHC and the highest rate of 3.30 per 1000 in the Quinte, Kingston, Rideau DHC), the variations remained at almost a 3-fold level and the correlation between percent rurality and pyloromyotomy rates remained unchanged. It is also important to note that the distributions of pyloromyotomy rates by DHC and rurality over the 2 time periods (1993-1996 and 1997-2000) were consistent, which indicated confidence that the observed pyloromyotomy rates could not be attributable to a random chance observation. Furthermore, the pyloromyotomy rate for the Quinte, Kingston, Rideau DHC was statistically significantly different from the overall provincial rate; therefore, this observation is solid because the probability that the difference observed is due to error or random chance is less than 5% (P<.05).