title: Emergency department visit volume variability.
abstract: OBJECTIVE
  One of the most important and basic variables in emergency department (ED) operations is patient visit volumes. This variable is usually predicted on the basis of the average ED patient visit volume over a certain period. However, ED patient visit variability is poorly understood. Therefore, we evaluated ED patient visit variability in order to determine if the average can be used to operate EDs.
  
  
  METHODS
  Nationwide ED patient visit data were from the standard emergency patient data of the National Emergency Department Information System. The data are transferred automatically by 141 EDs nationwide. The hourly ED visit volumes over 365 days were determined, and the variability was analyzed to evaluate the representativeness of the average.
  
  
  RESULTS
  A total of 4,672,275 patient visits were collected in 2013. The numbers of daily ED patient visits were widely dispersed and positively skewed rather than symmetric and narrow with a normal distribution.
  
  
  CONCLUSIONS
  The daily variability of ED visit is too large and it did not show normal distribution. The average visit volume does not adequately represent ED operation.
authors.affiliation: Department of Emergency Medicine, Jeju National University Hospital, Jeju, Korea.
authors.forename: Seung Woo
authors.initials: SW
authors.lastname: Kang
authors.affiliation: Department of Emergency Medicine, Jeju National University Hospital, Jeju, Korea.
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Park
keywords: Crowding; Efficiency; Emergency service, hospital; Management information systems