Examining the effect of decreasing mobile device information display size on procedural task performance

Keena S Byrd, Purdue University

Abstract

This thesis evaluated the ability of maintenance experts to use small, mobile, hand-held electronic devices to view and execute critical task procedures. Although advanced generation Personal Data Assistants (PDA's), Ultra Mobile Personal Computers (UMPCs), and other intelligent electronic displays are prevalent, many low-production, high-risk operations still display/present their procedures in a paper format. By using a handheld device rather than paper-based procedures at the National Aeronautics and Space Administration (NASA), volumes of information that would have previously obscured a technician's workspace or been difficult to organize in the field could be easily stored, manipulated, and shared. With recent technical advances, electronic devices have decreased in size; however, their interfaces have grown more complex. This complexity could cause cognitive overload, longer task completion times, and errors that affect performance if used in safety-critical environments. The first phase of this research establishes a minimum mobile screen size for use by expert technicians involved in safety-critical tasks, then phase two validates this screen size in NASA assembly operations. Phase One experiment compared task performance using three common small screen sizes: Ultra Mobile PC (7in/17.8cm), PDA (3.5in/8.9cm), and SmartPhone (2.8in/7.1cm). Results from 65 student participants indicated a significant difference in completion times between the three screen sizes (F(2,120) = 690, p < 0.050). There was also a significant difference in screen access time between the three screen sizes (F(2,91), p<0.001). Based on this data, the smallest screen size used to complete procedure-based tasks should not be less than 3.5-inches. The Validation Study in Phase Two of this research used 3.5-inches as a baseline screen size for investigating the utility of a handheld device in the complex assembly/production environment at Marshall Space Flight Center (MSFC) in Huntsville, Alabama. The maintenance expert's screen access and completion times were slightly less for the paper-based than the handheld displayed version of the procedure; however, the maintenance expert did not make any errors when using either version. The subjectively-assessed cognitive workload calculated by the average NASA-TLX score was marginally higher when the engineering technician used the paper-based procedure than when he used the electronic version. Since the evidence suggests that there could be important cognitive impacts resulting from extensive use of small screen displays, future work should further investigate the response variables that directly contribute to use of associative and procedural working memories. The validation study results suggest that MSFC technicians could benefit from handheld procedure presentation through easier access to sub-procedures and supporting documents; improved document maintenance and management; reduced paper and increased workspace.

Degree

Ph.D.

Advisors

Caldwell, Purdue University.

Subject Area

Industrial engineering|Cognitive psychology

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