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Chapter 5
the validity of the questionnaire, the domains of the questionnaire were compared with two corresponding paper-and-pencil-based questionnaires that were seen as ‘gold standards’ for the subjects of interest. The same question rises about whether or not all participants were able to autonomously complete these ‘gold standard’ questionnaires. If participants were assisted by a researcher, this may have created interviewer bias [53]. Another question that should be asked in this situation is whether or not the questionnaires that have been used as ‘gold standards’ can be seen as such for the target population of the TT. Paiva et al. reported that the ‘gold standards’ were previously validated [22]. The research population of the validation studies of one ‘gold standard’ was comparable on educational level to the study population of Paiva et al. [54]. The characteristics of the research population of the other ‘gold standard’ were not described in terms of educational level [55]. In both validation studies of the ‘gold standards’, nothing was reported about the reading and writing skills of the participants. People who had difficulties reading and writing were not actively excluded, but on the other hand no specific efforts were described that were made to include them either [54,55]. Therefore it is unknown whether or not participants with low (health) literacy were part of the study populations in the validation studies of the ‘gold standards’. This makes it uncertain whether or not the results of these studies are transferable to the target population of the TT of Paiva et al. Furthermore, only the validity of the paper-and-pencil version of the newly-developed questionnaire of Paiva et al. [22] was tested, and not that of the digital version. Looking at the results of the study presented in Chapter 4.1, it is necessary to test the validity of the digital version, because adding ICT to a questionnaire could potentially influence its validity.
STRENGTHS AND LIMITATIONS
Strengths
The research project described within this thesis was a typical practice-based research project [56]. It was set up and carried out with the help of eight physical therapists, working in deprived areas of Utrecht, Netherlands. The problems these therapists experienced with using PROMs within their patient populations was the direct reason for setting up this research project. Furthermore, the collaboration with ten designers with low literacy during the whole course of the
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