Workshops - UbiComp

a group of users. We, therefore, introduce the concept ofgroup user experience. In contrast to individual userexperience that describes an individual’s experience ofknowledge, culture, history or aesthetics, group userexperience describes the overall experience acquired by auser group, including not only each member’s directindividual experience but also the indirect experienceacquired through intercommunication among groupmembers. For instance, suppose that you are visiting amuseum together with several friends, you can acquireexperience from what you see, which is direct experience,and at the same time you can also acquire experience fromwhat your friends see through intercommunication withthem which is indirect experience. Group user experience isthe composite of both each group member’s directexperience and indirect experience.Apparently, different types of user groups would resultin different kinds of evaluation models of group userexperience. Consider tightly coupled heterogeneous usergroups, such as a family, children are superior to theirparents when they visit a museum because, as we havementioned above, parents do not care what they seethemselves so much as what their children see. From thispoint of view, the experience of children is just theexperience of their parents. Therefore, the evaluation modelof this kind of user groups should give a heavier weight tothe members with higher priority than the others and shouldtake the intercommunication among members into account.On the other hand, the evaluation model of loosely coupledhomogeneous groups should give the same weight to eachmember and should not calculate the intercommunication.In the following section, we will introduce a generalquantitative evaluation model of group user experiencewhich is suitable for different kinds of user groups.QUANTITATIVE EVALUATION MODEL OF GROUPUSER EXPERIENCEAt the beginning of this section, we list the notations to beused in the evaluation model as follows. G : a user group. u : a group member. i : a item. R( ui , ) : the rating for item i given by groupmember u . Impact( u, i ): the revised rating for item i given bygroup member u . Au ( ) : the items that have been visited by groupmember u . AG ( ): the items that have been visited by any memberof group G . Gi (): the members who have visited item i . Eui ( , ): the experience of user u acquired from itemi . Eu ( ): the direct experience of user u . Eu ( ) : the indirect experience of user u . EG ( ): the overall experience of user group G .Quantitative Evaluation of Individual User ExperienceWe first introduce the quantitative evaluation model ofindividual user experience. For quantitative evaluation,quantitative parameters must be selected in advance.Currently, the most widely used evaluation parameter isuser rating, which thereby is also adopted as one of theparameters in this paper. One hundred scales, from 1 (thelowest experience) to 10 (the highest experience), aredesigned for the value range of user ratings. To improveaccuracy, user ratings are revised via the following twosteps.Normalization. It is possible that an individual’s rating maybe too low or too high. This can be revised throughnormalization. We apply normalization to user ratings asfollow. Rvi (,)vG()iGroupAverRating() i | Gi ( )|, i A( u), (1) R( ui , )iA( u)IndividualAverRating( u)| Au ( )|, (2)R( u, i) GroupAverRating( i)Normalized( R( u, i)) , i A( u).IndividualAverRating( u)(3)In the above equations, GroupAverRating()i is theaverage rating for item i given by members of groupGi () and IndividualAverRating( u ) is the average ratingof user u .Making the rating quadratic. An investigation by Masthoff,J. showed that the relationship between user experience andthe ratings they give are not linear, that is, for example, thedifference between the rating 6 and rating 7 is not the sameas the difference between the rating 9 and 10. Quadratic is abetter measurement than linear [6]. We use the followingequation to apply quadratic.Quadratic( R(,)) u i R(,) u i R( u,)i . (4)Combining equations (3) and (4), we have the reviseduser rating Impact( u, i ) asImpact( u, i) Quadratic( Normalized( R( u, i))). (5)After revision through the above mentioned two steps,Impact( u, i ) is a more accurate evaluation parameter thanthe original user rating. However, even though two usersgive the same ratings to a certain item, it is still very likelythat their experiences on this item are different. This may becaused by several distinct factors, an important one ofwhich is the user attention duration. So, besides user ratings,we import the user attention duration as another evaluationfactor. In this paper, we introduce user attention duration41