| Summary: | <p>This research introduces the concept of transferability into the usability construct
and creates the Usability Paradigm for Multiple Device System (UPMDS) to
conceptualize and quantify the usability in multiple device scenarios. This study fills the
literature gap that no effective method exists in measuring transferability and in
quantifying usability in a multiple device context. This study also answers the research
questions regarding the impact of task complexity, user experience, and device order on
the total usability of the system.</p>
<p>Study one follows a systematic approach to develop, validate, and apply a new
questionnaire tailored specifically to measure the transferability within a multiple device
system. The System Transferability Questionnaire (STQ) is obtained after validation with
15 question items. In a software usability study, the STQ demonstrated excellent internal
reliability and validity. Results show that the STQ is effective in capturing four factors
regarding transferability, which are transfer experience (TE), overall experience (OE),
consistency perception (CP) and functionality perception (FP). Validation results show
good convergent, discriminant, criterion and nomonlogical validity.</p>
<p>Study two adopts a systematic tool to consolidate usability constructs into a total
usability score. The study utilizes principal component analysis (PCA) to determine the
weight of the four usability components (satisfaction, transferability, effectiveness, and
efficiency), which is used when obtaining the total usability score. Results show slightly
different weights for the four components. This quantitative tool can be applied in
different usability context in which multiple devices are involved. Usability specialists
are encouraged to adjust the tool based on different usability scenarios.</p>
<p>Study three investigates the impact of task complexity, user experience, and
device order on the total system usability. Results show that the total usability score is not
affected by task complexity, user experience or device order. However, lower physical
task complexity leads to longer performance time and lower errors from the users. High
experienced users have significantly lower errors made in tasks. The machine order also
has divergent results. When the mini-lathe machine was used first, users had better
transferability results but poorer performance outcomes as compared to when the drill
press was used first.</p>
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