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Abstract

A method for quantitatively and objectively measuring the usability of a system. The method provides quantitative measures for usability satisfaction, usability performance, and usability performance indicators. Usability satisfaction is measured by acquiring data from a system user population with respect to a set of critical factors that are identified for the system. Usability performance is measured by acquiring data for quantifying the statistical significance of the difference in the mean time for an Expert population to perform a task on a particular number of trials and the estimated mean time for a Novice population to perform the task on the same number of trials. The estimated mean time is calculated according to the Power Law of Practice. Usability Performance Indicators include Goal Achievement Indicators, Work Rate Usability Indicators, and Operability Indicators which are calculated according to one or more measurable parameters which include performance times, numbers of problems encountered, number of actions taken, time apportioned to problems, learning time, number of calls for assistance, and the number of unsolved problems. A task analysis and re-engineering methodology statistically compares quantitative usability measurements according to various classified subsets of the overall population. Such subsets or categories include population, critical factors, a critical factor, vital critical factors, other demographic groups, etc. Preferably, such subsets are set forth in a hierarchical manner such that the statistical comparison identifies a root task characteristic for re-engineering. Task analysis and re-engineering may also be performed according to activity on arrows, and activity in nodes techniques.

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