11.9.1 LA PROCREACIÓN Y LOS DERECHOS NATURALES DEL SER HUMANO

Auditory Vocal Tasks Visual Manual Tasks

Lower Workload _{Sports Broadcast HVAC}

In-Vehicle Tasks Book on Tape Listen Radio Easy

Book on Tape Summarize Radio Hard Biographic Q & A Cassette

CD/Track 7 Coins

Higher Workload Route Instruction Manual Dial

In-Vehicle Tasks Route Orientation Read Easy

Travel Computations Read Hard Map Easy Map Hard Route Tracing Destination Entry

Exploratory (Not Used): Voice Dial Delta Flightline

Figure 3-54. Task Classifications Used for Level 1 Discriminability Analyses Note: In these analyses, tasks in this matrix were all compared to Just Drive as a

lower-workload task since there was no subsidiary task at all.

3.7.2.2 Level 2 Discriminability Analysis

For Level 2 analyses, tasks were sorted into high- and low-workload categories, based on a combination of findings from the literature, analytical modeling, and expert judgment (See Chapter (2). These sorts are shown in Figure 3-55.

Chapter 3 Test Track Results

Task Classifications for Comparisons of Low and High Workload Auditory Vocal Tasks

& Just Drive Visual Manual Tasks

Lower Workload Sports Broadcast HVAC

In-Vehicle Tasks Book on Tape Listen Radio Easy

Book on Tape Summarize Radio Hard Biographic Q & A Cassette

CD/Track 7

Just Drive Coins

Higher Workload Route Instruction Manual Dial

In-Vehicle Tasks Route Orientation Read Easy

Travel Computations Read Hard

Map Easy Map Hard Route Tracing Destination Entry

Exploratory (Not Used): Voice Dial Delta Flightline

Figure 3-55. Task Classification for Level 2 Discriminability Analyses Note: In these analyses, tasks shown as high were compared to tasks shown as low

within each type of task. The Just Drive task was grouped as a lower-workload task within the auditory-vocal task set, due to the similarity of its length and performance profiles to these tasks. Like auditory-vocal tasks, Just Drive had no visual input demands from a subsidiary task or manual output demands from a subsidiary task.

If a task was judged to fall within the higher-workload category group than the comparison task, it was predicted that each subject’s pairs of task scores for these tasks, when compared, would result in a difference score that was positive (+), matching the predicted alignment (Task 1 greater than Task 2, on a given a metric, if that metric followed the expected “higher on the metric means higher-workload” pattern or Task 1 less than Task 2 for a “lower on the metric means higher- workload” pattern.). This directional hypothesis was then tested using a sign test. The sign test was applied at the per-participant level for each selected measure. For each participant, the difference was calculated between that person's performance measure on one task (e.g., Task A) versus that same person's performance measure on another task (e.g., Task B) under comparison. Only the sign of each difference per participant (+ if Task A > Task B; if Task A < Task B; or tie if Task A = Task B) was retained for analysis. The signs of the differences were tallied across all participants who performed both of the tasks (e.g., Task A and Task B) under comparison. The distribution of positive and negative signs (ignoring ties) was then evaluated statistically. The evaluation assessed whether the percentage of positive signs and negative signs was much different from 50-50 by chance. A directional sign test specifically looked to see whether or not the percentage was significantly different from 50-50 and in the expected direction. This method was used for both Level 1 and for Level 2 discriminability tests. The sign test examined ordinal differences between a person's performance on one task and another task. This is a very different level of analysis than group means, medians, percent misses, and the like. The test's main virtues

Chapter 3 Test Track Results

3-82

are its long history, simplicity, and its freedom from assumptions of normality, linearity, homogeneity of variance, and so forth.

The discriminability percentages were based on varying numbers of paired-comparisons. (Refer to Figure 3-54 for the breakout of CAMP DWM tasks into higher- and lower-workload categories based on prior prediction). The number of paired comparisons depended on whether Level 1 results were reported or Level 2 results were reported. The following numbers apply for Level 1 comparisons of visual-manual tasks to Just Drive. Visual-manual task discriminability percentages were based on up to 13 comparisons to Just Drive if all 13 visual-manual tasks were included. There were seven paired comparisons to Just Drive if only the seven higher-workload visual-manual tasks were included. There were six paired comparisons to Just Drive if only the six lower-workload visual-manual tasks were included. The following numbers apply for Level 1 comparisons of auditory-vocal tasks to Just Drive. Auditory-vocal task discriminability percentages were based on up to seven paired comparisons if all auditory-vocal tasks were included. There were three paired comparisons to Just Drive if only the three higher-workload tasks were assessed. There were five paired comparisons to Just Drive is only the five lower- workload auditory-vocal tasks were included. These numbers should be kept in mind when considering the Level 1 results.

Level 2 discriminability percentages were based on larger numbers of paired-comparisons. The visual-manual tasks provided seven higher-workload tasks, each compared against six lower- workload tasks. Thus, Level 2 visual-manual task discriminability percentages were based on 42 paired comparisons. The auditory-vocal and Just Drive tasks provided three higher-workload tasks, each compared against five lower-workload tasks. Level 2 auditory-vocal task discriminability percentages were therefore based on 15 paired comparisons. These numbers should also be kept in mind when considering the discriminability results.

3.7.3 Discriminability Results: Levels 1 and 2

Results of discriminability analyses for both Levels 1 and 2 are summarized in Table 3-13, Table 3-14, Table 3-15, and Table 3-16. Table 3-13 shows the results for driving performance metrics for visual-manual tasks plus a small subset of eyeglance measures to the not road location. For these measures a higher score on the metric was believed to indicate higher workload. Table 3-14 shows results for driving performance metrics for auditory-vocal tasks plus these few eyeglance measures. Table 3-15 shows results for eyeglance metrics for visual-manual tasks. Table 3-16 shows results for eyeglance metrics for auditory-vocal tasks. Percentages over 67 percent were highlighted in yellow, but 70 percent was used as a cutoff point for meeting the discriminability criterion.

Level 1 discriminability analyses are summarized for low-workload tasks versus Just Drive in the first column of Table 3-13 and Table 3-14, and are summarized for high-workload tasks versus Just Drive in the second column of Table 3-13 and Table 3-14. The third column summarizes “all tasks” versus Just Drive.

Level 2 discriminability analyses are summarized for high-workload tasks versus low-workload tasks in the fourth column of Table 3-13 and Table 3-14 for driving performance metrics.

Chapter 3 Test Track Results

Table 3-13. Summary of Level 1 and 2 Discriminability Results for Driving Performance Metrics Based on Test Track Data for Visual-Manual Tasks

Metric Low Workload In-Vehicle Tasks vs. Just Drive High Workload In-VehicleTasks vs. Just Drive All In-Vehicle Tasks vs. Just Drive Low Workload Tasks vs. High Workload Tasks

Lanex Cross Trial 0% 29% 16% 29%

MeanduratNR 0% 29% 16% 90% MeanglancesNR 0% 14% 8% 81% MeanmeanNRdur 83% 100% 92% 50% MeanpctdurNR 100% 100% 100% 45% PctMissCHMSL 83% 86% 85% 14% PctMissDecel 100% 57% 77% 2% PctMissFVTS 100% 100% 100% 2% SDLP 0% 43% 23% 74% Speed Diff 0% 14% 8% 88% Task Duration 0% 0% 0% 90%