This article is an answer to a commentary on Christophersen and Konradt’s (2011. Reliability, validity, and sensitivity of a single-item measure of online store usability. Int. J. Hum. Comput. Stud., 69, 269–280) study on a single-item measure of online store usability. The authors suggest that while their research has demonstrated the psychometric quality of their measure, greater efforts should be made to perform more rigorous tests of measures by applying main and supplemental psychometric quality criteria. In addition, it is suggested that future research should also (i) examine the type of construct by using formative and reflective measurement models; (ii) put forward relevant cognitive processes during answering questions and (iii) make use of behavioral and physiological data to complement user’s self-reports.

The aim of this study was to develop and validate a reflective and a formative measure of online store usability. Perceived usability, related constructs (i.e. trust and aesthetics), controls (i.e. user and product characteristics) and consequences (i.e. intention to buy and purchase) were examined within a nomological network. Three hundred and seventy-eight participants completed an experimental study. Each participant visited 2 out of 35 online stores and rated the usability and intention to buy for both stores. Purchase behaviour was determined by combining the participants' reward with the decision to buy. Results from partial least squares (PLS) structural equation modelling indicate that the formative usability measure forms a valid set of items for the user-based assessment of online store usability and that both measures are positively related to the intention to buy, suggesting criterion validity. As hypothesised, positive relationships of usability with trust and aesthetics were supported. Furthermore, both measures provided a good prediction of the decision to buy, indicating overall predictive validity. Limitations and implications for usability measures and human–computer interaction research are discussed.

This paper describes the development and empirical validation of a new scale for measuring usability in online shops, i.e. the Usability Questionnaire for Online Shops (UFOS1). Sixty users with different demographic characteristics were given the task of finding and ordering products in two out of six web shops. In addition to usability, shop response time, shop size, services, distinctiveness of products and trust were used as predictors with intention to buy and decision to buy as criteria. A factor analysis of UFOS revealed seven factors, consisting of general usability, accessibility of general conditions, product search, shopping-basket handling, process of ordering, product overview, self-descriptiveness and product characteristics. Results on intention to buy show that about half of the participants were not willing to buy online, and users with more experience in online shopping and a higher frequency of Internet use were more willing to buy online. A regression analysis of buying intention shows that usability has the greatest impact on buying intention, followed by the size of the shop and trust. A discriminant analysis reveals that usability and perceived size are the characteristics which contribute mostly to the decision to buy and correctly classify 91% of the decision to buy.