Geography Reference
In-Depth Information
4.3 The Experiments
Two experiments were conducted, based on the display in Fig.
2
a, which, when
considered in the context of the PCP, could be said to have a poor task-to-display
compatibility.
The first study (Wong et al.
1998
) reorganised the ambulance status display so
that it mirrored the relative geographical positions of the ambulance stations
(employing the PCP strategy of fostering spatial proximity—Wickens
1992
),
reinforced by line links on the display between stations that are connected on the
road network (another PCP strategy—Fig.
2
c), theoretically giving it a good task-
to-display compatibility.
To determine whether this display would result in improved dispatch perfor-
mance, an experiment was conducted where thirty-seven participants were asked
to respond to twelve simulated emergency calls that had four levels of difficulty,
i.e. (in order of increasing difficulty):
- simple problem (one incident occurs in a town with one ambulance)
- simple trade-off problem (one incident occurs within a station's catchment—the
station has more than one ambulance, hence the trade-off)
- boundary problem (one incident occurs half-way between two stations, each
with an ambulance) and;
- balancing problem (a major incident occurs, requiring multiple ambulances
from many stations, leaving gaps in coverage which in turn have to be filled).
Participants were randomly assigned to one of two screen design conditions (the
original screen or the modified screen). The participants were all novices to dis-
patch management and participated as part of a class requirement for a University
paper.
For the results, the performance of each display was represented by the time
elapsed between when the participant finished entering the call details, and when
the first ambulance was dispatched. A separate MANOVA (multivariant analysis
of variance) was performed on each of the different levels of task difficulty to
determine whether the mean differences in performance for each screen condition
was significant. Efficiency-wise, the results showed non-expert participants per-
formed approximately 40 % faster with the modified display than the original
display on the two more difficult levels of dispatch tasks (average dispatch speed
across all difficulty levels was 14.21 s with the old display as opposed to 10.21 s
with the new). Effectiveness results recorded errors made in 7.3 % of dispatch
tasks (old) as opposed to 5.1 % (new).
However, it was not clear from this study whether the performance improve-
ments were due to the reorganization of the screen or the lines. Therefore, a second
study (Hayes et al.
2003
) set out to determine whether it was the connecting lines
or the semantically compatible display organisation that was responsible for the
performance improvements.
