For instance search time may be key design criteria

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Unformatted text preview: s. The selection of the most appropriate metrics will depend on the form of system being tested. For instance, search time may be key design criteria for information retrieval systems, however for a general- purpose text editing system the users feelings, system security and enjoyment might be the most important in contrast with performance metrics. An overall evaluation of usability for an entire system may also be works out if this is considered to be important. Below is a table of possible measurement criteria defined by Tyldesley (1988) which can be used as guide for usability measurement. 31 Possible usability measurement criteria ________________________________________________________________ (1) Time to complete task. (2) Percentage of task completed. (3) Percentage of task completed per unit time (speed metric) (4) Ratio of successes to failures. (5) Time spend on errors. (6) Percentage number of errors. (7) Percentage number of competitors that do this better than current product. (8) Number of commands used. (9) Frequency of help or documentation use. (10) Time spend using help or documentation (11) Percentage of favorable: unfavorable user comments. (12) Number of repetitions of failed commands. (13) Number of runs of successes and of failures. (14) Number of times the interface misleads the user. (15) Number of good and bad features recalled by users. (16) Number of available commands not invoked (17) Number of regressive behaviors. (18) Number of users preferring your system. (19) Number of times users need to work around a problem (20) Number of times the user is disrupted from a work task (21) Number of times the user loses control of the system. (22) Number of times the user expresses frustration or satisfaction. ______________________________________________________________________ Table 2.2 Possible measurement criteria (adopted from Tyldesley, 1988) Source: (Preece, 1995) Page 405 2.8 Usability Principles for WAP Services 2.8.1 Usability Principles for WAP Services defined by Ramsay (2001) Ramsay (2001), conducted a detailed WAP usability test and figured out various aspects of improvement from users point of view, in terms of the five attributes of usability - Learnability Efficiency Memorability Few errors and Satisfaction 32 WAP did not perform very well. WAP enabled phones are not very difficult to learn and to use, and once the keys are learnt and functions used, it does not easily forgotten. However, for higher levels of performance the story is quite different. Users experienced too many lost connections and poor signpost to be able to get to grips the system with any real efficiency. Errors, should be fewer, however errors has plagued the system. User satisfaction was found generally very poor, in terms of being pleasant to use system. Ramsay (2001) recommended five usability principles to improve WAP services which are as following: 1. Poor errors massage handling According to WAP study of Ramsay (2001), he point out that the users were usually unimpressed with error messages handling whenever that came up on screen in case of connection loss or drop. Users encounter meaningless and confused types of errors such as, internal server error, downloading stopped due to time out etc. The users were found often unhappy because they were unable to understand nature and cause of these errors. Are these errors occurring due to their own mistake or is it something wrong at server? Therefore, error massages need to be clear and meaningful to help WAP user. 2. E-Navigation and Labeling Ramsay (2001) reveals that E-Navigation and Labeling are two major issues. In contrast, the networks and content providers offered broad lists of sites and services by proving that everything a WAP user may need, however, for the users this is a recipe for disaster. The long manus required thumb-numbing and scrolling. Categories are good way to sort information but once the user clicked through the guiding role of the screen is often found abandoned. Therefore, overall user experience was not satisfactory. 3. Unnecessary browse time Time is big money on WAP. Any website that is easy to browse and presents its information clearly is one that the users will like to return again and again; however, in fact such sites are rarely in seen. Generally all major WAP sites took unnecessary time to browse and display information (Ramsay 2001). 4. Minimize input Ramsay (2001) suggested that WAP sites should be designed in a way to minimize user input. In order to fix this issue, WAP products should be offered as preset choices, so that user just needs to browse and select the required information. 33 5. Help Facility According to Ramsay (2001), help facility should be offered at all WAP sites, so that user can get an assistant as per situation. 2.8.2 Usability Principles for WAP Services defined by Condos et al. Condos et al., (2002) conducted a WAP usability study during Nov. 2001 and Feb. 2002. The purpose of the study was to reports the findings of a WAP usability study, which comprises an assessment...
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