Practical considerations make subjective opinion one of the most widely used methods to assess mental workload. However, the value of the data obtained by subjective methods is often limited because scales are not standardized and are not based on modern psychometric principles. This paper describes the development and validation of a Subjective Workload Assessment Technique (SWAT) which uses conjoint measurement to construct interval level workload scales from ordinal rankings of combinations of levels on three contributory dimensions. An experiment was conducted to investigate the construct validity and concurrent validity of the SWAT-1 scale. Recommendations for further development are discussed.
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