Quotation Dexter, F., Macario, A., Epstein, R.H., Ledolter, Johannes. 2005. Validity and Usefulness of a Method to Monitor Surgical Services' Average Bias in Scheduled Case Durations. Canadian Journal of Anesthesia 52 (9): 935-939.




Unbiased prediction of case durations is an integral part of matching operating room (OR) staffing to workload. Monitoring systematic bias in surgeons' scheduled case durations can identify those services with estimates sufficiently inaccurate that statistical analysis of historical data may be useful in preference to the surgeons' estimates. We describe a method to monitor surgical services' average bias in scheduled case durations. METHODS: Actual case duration, predicted (scheduled) case duration, and service were obtained for all 58,291 cases during 39 four-week periods at an academic hospital. For each four-week period, a ratio was computed for each service. The numerator for each service equalled the sum of the differences in minutes between actual case duration and scheduled case duration. The denominator equalled the sum in hours of the actual durations of all of the service's cases. The ratio was multiplied by eight hours to yield the number of minutes of underestimated case duration per eight hours of OR time during the four-week period. RESULTS: The ratios followed a normal distribution for each service. Using the Student's t distribution, the 95% lower confidence bounds for the average underestimate of case duration ranged from three to 65 min per eight hours of used OR time. CONCLUSIONS: To reduce over-utilized OR time, we recommend monitoring each service's 95% lower confidence bound of the bias in scheduled case durations. For services consistently underestimating their case durations, schedule their cases using statistical estimates of case durations based on their historical data, and disregard their own estimates.


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Publication's profile

Status of publication Published
Affiliation WU
Type of publication Journal article
Journal Canadian Journal of Anesthesia
Citation Index SCI
Language English
Title Validity and Usefulness of a Method to Monitor Surgical Services' Average Bias in Scheduled Case Durations
Volume 52
Number 9
Year 2005
Page from 935
Page to 939
URL http://www.ncbi.nlm.nih.gov/pubmed/16251558


Ledolter, Johannes (Former researcher)
Dexter, F. (United States/USA)
Epstein, R.H.
Macario, A.
Institute for Statistics and Mathematics IN (Details)
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