THAAD User Interface Design

Program Manager, July-August, 2001 by Maj. Dan Wiley, Dr. Chris B. Grounds

Step 3 involves the development of the candidate screen prototypes proposed in Step 2 (Figure 2). Rapid prototyping tools aid in quick development of functional prototypes for experimental testing. Many times, a baseline screen already exists. This screen serves as the baseline for testing along with one or two alternative screens.

Step 4 involves the experimental testing of the screens prototyped in Step 3. Experimental testing is superior to feedback-based assessments in that the performance of the operator is used as a factor in making decisions about the best real-time interface rather than relying strictly upon preferences and opinions of the operators. Usually, a full factorial experimental methodology is used for experimental purposes, i.e., all the soldiers being tested perform all the tasks on all the screens to be tested.

In some circumstances, depending upon the time it takes to test or the amount of preparation required to switch between test requirements (e.g., Mission Oriented Protective Posture [MOPP] 0 vs. MOPP 4), soldiers will test using blocked procedures, i.e., half the soldiers test using alternative 1, then alternative 2; and the other half test using alternative 2, then alternative 1. Typically 16-20 soldiers are required to collect sufficient data for statistical power purposes (i.e., ensuring that collected data are representative of the larger THAAD user population). Data are typically collected over a two-day period (8-10 soldiers per day).

Step 5 involves analysis of the time and accuracy data collected during the experimental testing. Data are reduced to soldier number, performance time (in seconds) for each particular trial, and number of errors committed during that trial.

Step 6 involves making recommendations based on the results of statistical analysis. The following situations can occur:

* If an alternative prototype screen has been statistically proven (95 percent confidence) to be superior to the baseline screen, then a recommendation will be made to replace the baseline screen with the alternative prototype.

* If the baseline screen has been statistically proven to be superior to the alternative prototype(s), then a recommendation will be made to keep the baseline screen.

* If no prototype has been statistically proven superior when compared to the other prototypes, then a recommendation will be made to keep the baseline screen. If this occurs, however, it may prove valuable not only to incorporate the best features of the alternative prototypes into improving the baseline, but also to incorporate any valid suggestions from the soldiers.

Benefits of the Process

THAAD has capitalized on human-centered design, particularly by incorporating experimental testing, resulting in several benefits. First, human-centered design is an effective method for incorporating the soldier voice (qualitative and quantitative) in the screen design process. Second, it reduces the need for expensive design changes due to poor usability of the product by taking the human user into account in a timely manner during the design cycle. Third, it removes guesswork in defining the best screen for a particular real-time function by analyzing the soldier's performance in terms of decision time, action time, and accuracy for candidate screens. Finally, it increases the probability that THAAD soldiers will positively accept THAAD interface because their concerns, desires, and preferences are being taken into consideration from Day 1 of development. In particular, the usability testing that takes place in Step 4 has proven to be a valuable input into the BM/C31 design. Some results of this testing fo llow: