The Research On The Effectiveness Of SHERPA Method In The Evaluation Of Website Usability

Hierarchical task analysis（HTA）,as one of the task analysis methods,has been used for along time,and its validity on assessment has also been proved. Systematic Human ErrorReduction and Prediction Approach(SHERPA),a method being put forward on HTA, predicterrors of each process on the basis of the hierarchical analysis on the task. Initially, the methodis mainly used to predict the potential man-made errors in the industry so as to make a solution.In this paper, the method is applied to evaluate the usability of a website. By predicting thepossible errors in the process of using the web interface, we can evaluate the design of the webinterface reasonable or not.During the study,a real website is selected to make errorpredictions,and then the website is redesigned according to the predicted errors.By comparingthe usability of the pre-website and the redesign one, the the effectiveness of the proposedmethod is verified.There are three studies in this paper, including an investigation,a focus group study andthree experiments. Specifics are as follows:Study1: Improve SHERPA error classification in accordance with the website environment.Investigation1: Summarize usability guidelines and common errors of the website designing byconsulting documents.Focus group: Modify the classical SHERPA error prediction table in term of the usability of thewebsite by using the method of experts focus group.Study2: Study the feasibility of SHERPAin the website usability evaluation.Experiment1: Use the improved SHERPA to predict mistakes in the design of12306,in whichmay easily have mistake.Experiment2:Use typical task method to get the typical errors when people use12306.Comparethe results with the prediction by SHERPA so as to examine the feasibility of using SHERPA in website environment.Study3: Verify the availability of SHERPAin the website usability evaluation.Experiment3:Redesign the interface of12306according to the results of Study2.Then verify theeffectiveness of the redesign interface by using typical task method to get the performanceindicators,such as task completion rates, page residence time and the evaluation of users.Study two drawn using SHERPA prediction can predict most of the observed errors,and thefalse alarm rate is very low,which shows that the SHERPA method can effectively predictthe errors of interface design.We get an improved12306website by solving the problem.And the results of using typicaltask method task method are indicated that using the SHERPA method can improve the usabilityof websites effectively,the details as follows:(1)Supervisor experience satisfaction of the redesigned page on registration,query andbooking is much higher than the previous one.(2)The dwell time in the redesigned page is much shorter than the previous one,except theconsiderations page.(3)The time spending on registration,query and booking is shorter than the previous one.