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

97scared of their PIN being spying. Regarding face and soft biometrics, two users reported not to befully comfortable to be captured by a camera in front of colleagues. It is interesting to comparethe two scenarios (see Figure 8.3 with Figure 8.4), where the task was basically the same, given adifferent environment. The ratings though are partly significantly different (see FP and PIN).Figure 8.4: User preference of access methods in crowded environment: MOS and confidenceintervals for a confidence of 0.95.8.2.3 Time to Acquire, Ease of Use and Data SecurityTo evaluate statistical significance of the differences between the access methods, we performedadditionally Wilcoxon tests [Sie56], due to the relatively small sample size. Hence weasked users to rank the four access methods (1 to 4, 1 being the number one) in terms of speed,ease to access and data security. For the following graphs, the smaller the bars are the better theaccess method was ranked.Figure 8.5: User comparison of presented access methods in terms of speed, simplicity and datasecurity: MOS and standard deviation. Small bars represent high rankings.In terms of acquisition time and simplicity soft biometrics were ranked significantly better thanthe other methods. In respect to privacy, users were made aware that their data, in particular faceimage, list of soft features, PIN and fingerprint, would be stored on a database. This data can beon the one hand misused by operators, and on the other hand hacked. Users felt most comfortablewith providing both, PIN or a soft biometrics based list for storage on a database. Users wereambiguous about which they found is the riskiest trait to give away, fingerprint or a face image.8.2.4 Ranking of favorite access methodsThe last question regarded the overall satisfaction of the methods. Users named in this contextdifferent priorities. On the one hand privacy preservation was named by three users as justificationfor their ranking, on the other hand the easiness of use. The results on this ranking are displayed in