from ,,very bad" (1) to ,,very good" (7) on average with 5.6. As can be seen from table 3, ISONORM 9241/10 significantly correlates with the other two user-oriented questionnaires.
EVADIS II is a comprehensive evaluation system to be used by experts in the field of software ergonomics ( Reiterer & Oppermann 1993). For the validity study 13 different software systems were evaluated by a specialist in software ergonomics together with an experienced user of the software. Each evaluation session lasted approximately three hours. A subsample (N=383) of the full sample was used for this analysis. Each software was evaluated by 29.5 users on average, Nmin. = 11, Nmax. = 79. The correlation between EVADIS II and the mean ISONORM 9241/10 judgements was r = .59 (p < .01, N = 13 software programs).
This shows that the user-oriented questionnaire generates results similar to the outcomes of the expert-evaluation system, but with much less effort in time and money.
In this paper the software evaluation instrument ISONORM 9241/10 was introduced, and some reliability and validity results were presented.
The reliability ( Cronbach's alpha and re-test reliability) as well as the validity yielded satisfactory results. A further advantage of ISONORM 9241/10 is that it was constructed on the basis of an international standard. Therefore, it is likely to become internationally accepted. The questionnaire ISONORM 9241/10 is currently available in German ( Prümper & Anft 1997), Dutch ( Prümper & Anft 1998) and English (Prümper & Anft 1999). Further translations are in the offing.
ISO 9241-10 ( 1995). Ergonomic requirements for office work with visual display terminals (VDTs) - Part 10: Dialogue principles. Brussels: CEN - European Committee for Standardization.