Analysis Techniques For Man-Machine Systems Design

NATO UNCLASSIFIED -AC/243(Panel 8)TR/7 108 ^Volume 25.6 NASA TASK LOAD INDEX (TLX)WEWhat the technique doesThe T1LX is a multi-dimensional subjective rating procedure that provides an overall workload score based on the sumof the weighted values of six sub-scales: mental demands, physical demands, temporal demands, own performanceeffort, and frustration. The first three subscales relate to the demands imposed on the subject by the task, and thesecond three relate to the interaction of the subject with the task.Each subscale ranges from 0 to 100 and can be scored in steps of 5 points. Typically, the ratings are made bymarking a line. The degree to which each of the six factors contributes to the workload of a particular task isexpressed by the weighting applied to each subscale. Those weightings are derived from the subjects' pair-wisecomparisons of thesix subscales. The weights can range from 0 (all other subscales are more important) to S (noother subscale is more important).SCALEENDPOINTSTable 5.6:TLX workload subscalesTDESCRIPTIONmental demand low/high How much mental and perceptual activity was required (e.g., thinking,deciding, calculating, remembering, looking, searching etc.)? Was thetask easy or demanding, simple or complex. exacting or forgiving?physical demand low/high How much physical activity was required (e.g., pushing, pulling,turning, controlling, activating etc.)? Was the task easy or demanding,slow or brisk, slack or strenuous, restful or laborious?temporal demand low/high How much time pressure did you feel due to the rate or pace at whichthe tasks or task elements occurred? Was the pace slow and leisurely orrapid and frantic?performance perfect/failure How successful do you think you were in accomplishing the goals ofthe task set by the experimenter (or yourself)? How satisfied were youwith your performance in accomplishing these goals?aresin)RtTRaeffort low/high How hard did you have to work (mentally and physically) toaccomplish your level of performance?frustration level low/high How insecure, discouraged, irritated, stressed and annoyed versussecure, gratified, content, relaxed and complacent did you feel duringthe task?Inputs to the techniqueOutputs of the techniqueUsers need practice in using the technique, as well as a Scores of workload on the six subscales and an overallgood understanding of the mission, function and tasks to score of workload based on the sum of the weightedbe performed.subscales.NATO UNCLASSIFIED- 108 -