Optimal Design of Event Lists (ODELs) Phase 2

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Authors: Vicki Ahlstrom
Bonnie Kudrick

Ahlstrom, V., & Kudrick, B. (2006). Optimal design of event lists (ODELs) phase 2: Does list length impact performance? (DOT/FAA/TC-06/13). Atlantic City International Airport, NJ: Federal Aviation Administration William J. Hughes Technical Center.


This report documents the second study on the optimal design of event lists (ODELs). This study investigated the impact of event list length on user performance in searching for information. Participants searched for information in each of four different lists, each with a different length: 5 items, 15 items, 25 items, and 35 items. Researchers measured task completion time, accuracy, subjective ratings, and rankings. The shortest list (5 items) led to significantly slower response rates. The slower response rates appear to be due to the time it took users to scroll through the table. Participants made significantly more errors on the longer lists than on the shorter lists. Subjective data mirrored the performance data. Users preferred the mid-size lists (15 items and 25 items) and rated them higher than the longest list (35 items) and shortest list (5 items). Based on the results of this ODELs study, we would recommend a list size of 15 or 25 items over a list size of 5 or 35 items if speed and accuracy are important to the task.