Analysis Techniques For Man-Machine Systems Design

NATO UNCLASSIFIEDAC/243(Panel 8)TR/7 56Volume 23.4 FUNCTION ALLOCATION EVALUATION MATRIXWhat the technique doesThe technique sums weighted scores of human and machine capabilities to make function allocation decisions.Candidate sub-system functions are listed and compared against the capabilities of hardware, software, and humans.The form used to record these comparisons is called afunction allocation screening worksheet (see example, Figure3.3). Such worksheets are constructed by listing each of the several functions to be allocated on the left side of theworksheet. Two sets of evaluation criteria are listed across the sheet, as columns. The first set of columns listsoperator capabilities; the second set of columns lists equipment capabilities.Each of the candidate system functions is compared with inherent capabilities of hardware. software, or humans, usingthe kind of criteria contained in the Fius' List, previously described. Numerical weightings are assigned for eachcriterion, relevant to the system being analysed. These weighLings can include additional factors such as cost oravailability. The weightings can be derived from subject matter experts (SMEs). Mcister (1985) desciibes thedevelopment of such weights using a paired comparison technique. Each factor is compared with each other, in amatrix, and given a tally of I (if more important than the other factor) or zero (if less important than the other factor).The tallies are summed for each factor, and factor weightings derived from the sums as a percentage of the totalnumber of tallies.Once the weightings are established, the functions are reviewed in turn. Whenever an evaluation characteristic isapplicable to a specific function, a numerical score is assigned. The score is then multiplied by the weighting factor.The original and weighted scores are entered in the row/column intersection. The evaluation is completed bysumming each of the weighted scores for the "operator" and the "machine" allocations. If the weighted score total ismuch higher for one or other type of sub-system. the function is allocated to either "operator" or "equipment." Whenone of the weighted score totals is more than 80% of the other, then the allocation is made to "both" operator andmachine.Inputs to the techniqueBesides the candidate sub-system functions, the analystrequires information on the limitations of humanoperators, the state-of-the-arE performance of hardwareand software, and estimates of the system performancerequirements in terms of speed, accuracy, load, andreliability.Outputs of the techniqueThe outputs are the functions allocated to operator,hardware, and software. The results of the functionallocation trade are used to: a) determine the impact of crewtasks, skills, and information needs; b) appraise relatedcrew task capabilities and limitations; c) identifycorresponding display and control concepts; d) trade-offspecific sub-system performance capabilities; and e)perform task analysis and workload evaluations.When to useThe technique should be used during concept development and preliminary design. It can also be used during detaileddesign, to examine function tradeoffs. The technique should be used following a function analysis, and prior to a taskanalysis.Related techniquesThe technique is related to systems engineering function trade-off analyses, which are sometimes conducted to allocatefunctions to specific sub-systems.NATO UNCLASSIFIED-56-