Page 396 - Sensing, Intelligence, Motion : How Robots and Humans Move in an Unstructured World

RESULTS—EXPERIMENT TWO 371

TABLE 7.13. ANOVA Results for Completion Time: Interface and Visibility
Factors, RtoL Task
ANOVA Effects Studied: 1—interface, 2—visibility
df MS df MS
Effect Effect Effect Error Error F-Value p-Level
1 1 4336700.0 92 71092.52 61.00080 0.000000
2 1 24833.0 92 71092.52 0.34930 0.555959
12 1 58115.0 92 71092.52 0.81746 0.368286

reconciles with test observations: For both visible or invisible tasks the com-
pletion time in the physical task was significantly shorter than in the virtual
task. Similarly, for both physical and virtual tasks the completion time in the
visible environment shows no significant difference from that in the invisible
environment.

7.5 RESULTS—EXPERIMENT TWO

Recall that Experiment Two was designed to analyze the effect of subjects’
training and the related effect of the visibility factor on human performance. A
total of 12 subjects appeared in this study. In the first group, which included
six subjects, on day 1 each subject was subjected to six different training tasks,
plus one test task at the end, all in the visible environment. About one week
later, on day 2, the same subjects performed the same six training tasks, plus
the same test task, this time in the invisible environment. In the second group,
the remaining six subjects did the same tasks in the opposite order—that is,
tests in the invisible environment on day 1 and tests in the visible environment
on day 2. The specific task was right-to-left movement of the arm, the same
as in Experiment One (recall that this is a more difficult task compared to the
left-to-right task).
We therefore have a training factor Day, with two levels, day 1 and day 2.
Subjects were expected to learn the motion planning skill through a repeated
exercise.
Similar to Experiment One, human performance was measured by the path
length and completion time for each of the tasks Path and Time. Path length
is the measure of motion generated by the arm manipulator during the task.
Completion time is the time it takes the subject to complete the task. Both
measure the subjects’ proficiency in carrying out motion planning. We suppose
that both the path length and the completion time may be affected by such factors
as training and visibility of the scene, and we would like to quantify those effects.
In statistical terms, the training and visibility factors are independent vari-
ables, whereas the path length and completion time are dependent variables. The