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38
Chapter 3. Pilot Studies: Lessons Learned from Early Projects
Assembly Task
For our experiments we used a standard flat-pack wardrobe (model PAX, IKEA.
To make tests possible we needed to use a setup complex enough to allow several
assembly paths in a reasonable amount of time. In addition, the setup should
allow for errors during the assembly. To meet these requirements we decided to
use only three parts of the full wardrobe: one side-board and the upper and lower
horizontal boards. As the two horizontal boards are exactly the same, they positions
can be interchanged. Figure 3.4(a) shows the two possible ways of assembling the
component.
Methodology
The study was carried out with 20 participants with di erent backgrounds. 14
of the participants were male, 6 female. The average age of the participants was
26. The overall goal was to compare the usability and e ectiveness of classic paper
instructions with our microprocessor-based approach. To this purpose, we compared
the assembly time with classic instructions and with the LED-enhanced setup. The
participants were divided into two equally-sized groups for either approach. After
the initial performance comparison, the participants were encouraged to perform
the setup again three times using instructions presented in di erent modalities. The
first modality employed only the LED’s to display the instructions. The second
modality displayed interactive instructions on a computer screen. The information
for the instructions was based on the same sensor setup as with the LED’s. The
third modality extended the LED’s with (auditory) spoken instructions. Finally,
subjects completed a post-experiment questionnaire including questions comparing
the di erent modalities and classic paper instructions.
Results
To check whether there is a direct e ect of the di erent instructions on the as-
sembly performance, we measured the assembly time of the two groups. Using a
between-subject one way Analysis of Variance (ANOVA) on the task completion
times, showed that the values are significant on the 0.01 level (p=0.0067). This
statistical test shows that there is a strong tendency that the LED based instruc-
tions lead to a faster completion of the task (see
[
Antifakos et al. 2004
]
for further
details). Besides measuring the performance time, all errors that occurred during
assembly were noted. The only errors encountered were that four participants tried
to tighten the screws in the wrong direction. Two subjects using the classic instruc-
tions ended up with an uncompleted assembly because of this error. For LED-based
instructions, two other subjects noticed that something was wrong as the LED’s did
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