FACIAL SOFT BIOMETRICS - Library of Ph.D. Theses | EURASIP

94 8. USER ACCEPTANCE STUDY RELATING TO SOFT BIOMETRICS8.1.1 Testing MethodologyTest Setup : A set of 15 users (5 female, 10 male) of different nationality and ethnicity between26 and 37 years old was randomly selected from an office complex with the condition to notwork on biometrics. The participants were not paid. The test was consistent with the ITU-Trecommendation [usa00], that is to say we followed methods for interactive user tests of setting,equipment and environment, as well as subjects training and solicitation of opinions. We usedrating methods according to the absolute category rating (ACR). Specifically for the ratings of thefour access systems we presented each one at a time and let the user rate them independently. Wedenote this rating as MOS (mean opinion score), which spans on a five grade scale, five being"excellent" and one being "very poor". The user study took place in a computer laboratory, withsimilar conditions to an office. The duration per test was about half an hour. We performed aWizard of Oz study, see [Nie93], specifically the employed interfaces were functional, howeverthe acquired data was not processed. Hence processing time evaluation is not part of this study,neither the verification accuracy of the presented methods. The employed laptop was a DELLE4310. The documentation of the study contains the notes of questionnaires and related observernotes.Figure 8.1: Interfaces of the soft biometrics, face, PIN and fingerprint based access methods.Procedure : The four access methods, see Figure 8.1, were presented and demonstrated by theobserver of the study. Additional information on the methods, as of the differences between themethods, was provided. Subsequently participants of the user study freely explored the availablesystems. In the next step users were asked to log in with each of the systems. Subsequentlyan interview about the user experience was conducted. Here users were asked to absolutely rate(from 1 to 5, 5 being excellent) and comment on different aspects (easiness, clarity, comfort andspeed of the methods). Then users were confronted with two scenarios, where in the first scenariothe user accesses his/ her personal computer; whereas in the second scenario the user acquiresthe right of entry for a lab in a crowded corridor. The suitability of the methods was enquiredfor both scenarios. Additionally to the absolute ratings the users were asked to rank the methodsin terms of speed, easiness, privacy preservation and overall satisfaction. Finally the users wereinvited to select freely one method to log in with a task to read a file. This preference was notedas spontaneous and practical preference. In the following we give details on the different accessmethods.8.1.2 Access methodsWe selected four substantially different accessing methods, in terms of both, interface andtechnology, namely soft biometrics, face, PIN and fingerprint based access. In consent of recommendationsfor user friendly human computer interfaces (see [BH90], [CG05] and [Nie93]) wedeveloped four access systems, see Figure 8.1. All four interfaces were designed to be similar interms of structure and processing time in order to place emphasis on the four interaction elements: