Abstract #300489

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JSM 2003 Abstract #300489
Activity Number: 98
Type: Contributed
Date/Time: Monday, August 4, 2003 : 9:00 AM to 10:50 AM
Sponsor: Section on Teaching of Statistics in the Health Sciences
Abstract - #300489
Title: Statistical Modeling of EMS Rescue Calls
Author(s): Martin L. Lesser*+
Companies: North Shore LIJ Research Institute
Address: 1A Howland Rd., East Rockaway, NY, 11518-1616,
Keywords: Poisson process ; emergency medical services ; memoryless property
Abstract:

The frequency of rescue calls varies considerably. Calls may cluster together or have long intervals between calls. This study examined a statistical model to explain rescue call patterns. We analyzed the timing of all 658 rescue calls for 1999 in the E. Rockaway Fire Dept. Rescue Squad. Since the "Poisson process" (PP) model is known to describe "random" events, this model was tested. Mean number of calls/day was 1.8 or, 0.075 calls/hr. Mean time between calls was 13.3 hrs. A histogram and goodness-of-fit test suggest a Poisson distribution. Graphical analysis shows that the time sequence of calls behaves like a PP, which has the "memoryless" property for time between calls. The fitted model shows that the probability that 2 rescue calls occur within 1 hour of each other is 7.2%; within 1-2 hours 6.7%; more than 24 hours apart 16.5%. Rescue call patterns behave like a PP, which is consistent with statistical theory. Based on the fitted model calculations about the timing of rescue calls (e.g., number of calls in a given interval of time) can be made. This example can be used to introduce students to the Poisson process.

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