Task Satisfaction Index ( TSX)


The TSX is a subjective workload assessment tool. The TSX allows users to perform subjective satisfaction assessments on operator(s) working with various human-machine systems, therefore rating task, procedure or equipment.

The TSX is a multi-dimensional rating procedure that derives an overall workload score based on a weighted average of ratings on six well established sub scales (NASA TLX). These sub scales include Mental Demands, Physical Demands, Temporal Demands, Own Performance, Effort and Frustration.

With the weight of the workload establish, The TSX further rates the workload factor in function of an established subjective satisfaction scale. This sub scale includes: Very Satisfactory, Satisfactory, Marginally Satisfactory, Unsatisfactory, Very unsatisfactory and Unacceptable.

The end result provides a well defined weighted satisfaction rating.

Further more The TSX provides a final report weighted graphing tool.

The TSX can be used to assess workload in various human-machine environments such as aircraft cockpits, command, control, and communication (C3) workstations; supervisory and process control environments; simulations and laboratory tests.  The TSX is based on the NASA TLX study and findings. Information on the NASA TLX can be found at http://humansystems.arc.nasa.gov/groups/TLX/

The TSX rating scale works on the same principle as the the Cooper-Harper Rating Scale for Aircraft Handling Qualities. The TSX suggests additional values which provides concrete examples of scale values.

Test pilots use this type of rating procedure to provide subjective evaluations of the handling qualities of aircraft and aircraft simulations. They are "calibrated" by experiencing different levels of aircraft handling qualities in variable stability aircraft.

In the same way The TSX provides concrete experiences as references for each of tile 7 satisfaction scale values. By providing examples of tasks designated as very satisfactory to unacceptable, combined with a deficiency rating scale, the subjective rating variability is greatly reduced. To complete the Operational Test & Evaluation, the satisfaction rating scale is linked with a deficiency rating scale, and recommendation.

Deficiency rating:

Acceptable Satisfactory

  1. 1.Very Satisfactory                                    Meets or exceed all mission requirement   

  1. Desired or clearly adequate performance is attainable without operator compensation

  1. 2.Satisfactory                                              Meets all mission requirements

  2. The performance was good enough without improvement

  1. 3.Marginally satisfactory                             Meets mission requirements

  2. Only minor deficiencies were exposed.

Acceptable Unsatisfactory

  1. 4.Marginally unsatisfactory (Desirable)    Minor deficiencies- Some mission restrictions

  1. The operational tasks can be performed but could be improved or maintenance requirement could be reduced

  1. 5.Unsatisfactory (Highly Desirable)           Major deficiencies- Seriously degrades mission

  2. The operational tasks cannot be performed with the efficiency considered appropriate for the role or Significant maintenance requirements are likely to be reduced.


  1. 6.Very Unsatisfactory (Highly Desirable)   Major deficiencies-Seriously degrades mission

  2. The HMI has deficiencies that degrades performance, effectiveness, safety, reliability or maintainability. The crew is still capable of accomplishing the mission with an acceptable level of safety.

  1. 7.Unacceptable (Must be fixed)                    Major deficiencies- Unsafe / Unusable

  1. The airworthiness of the aircraft is affected;

  2. The operational tasks for which clearance is required either cannot be performed or can only be accomplished by the use of exceptional skills or in exceptionally favourable circumstances;

  3. Operational availability is estimated to be inordinately degraded by the incidence of defects or excessive maintenance requirements; or

  4. Important specification requirements are not met.



The weighted combination of factors provides a sensitive indicator of the overall workload between different tasks and among different levels of each task, while the weights and the magnitude of the ratings of the individual scales provide important diagnostic information about the specific source of loading within the task.  

The weighted combination of factors is directly linked with the magnitude of the ratings of the individual scales provide important diagnostic information about the specific satisfaction.