Modified Cooper-Harper Scale (MCH)

Modified Cooper-Harper Scale (MCH)

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Description

The modified Cooper-Harper Scale (MCH) is a subjective self-assessment method.

The controllers rate their experience of the exercise on a ten-point scale:

Level Description
10 Impossible
9 Intense Effort: Many Errors left
8 Maximum Effort to avoid large errors
7 Maximum Effort for moderate errors
6 Maximum Effort for adequate performance
5 High Effort
4 Moderate Effort
3 Acceptable Effort
2 Low Effort
1 Minimal Effort

Discussion

Cooper and Harper (1969) devised the scale which bears their names as a method of measuring the handling characteristics of aircraft by experienced test pilots. Williges and Wierwille (1979) suggested that it could be used as a measure of the mental workload involved in the task of flying. The modified Cooper-Harper scale (Wierwille et al. 19850 adapts the wording of the original scale to apply to more general tasks than flying an aircraft.

References

Categories
Human Factors Methods
Generics
Type of method Subjective
Data derived from controllers’ responses.
Target of method Workload
MCH can be used, in principle, on-line. It is particularly useful where workload varies during a task, and may experience peaks.
Time Scale of method Minutes
Portability of method Yes
Only paper forms and briefing material are needed for the MCH, so that it can be carried out anywhere.
Observer Effect No
Context of studies
Laboratory studies Use
 
Simulation studies Use
 
Field studies Use
 
Potential problems with the method
Failure risk Low
If the controller is not able to make a MCH rating, this is probably because he is in level 9 or 10 of difficulty. Where possible, as with the ISA test (QV) the time taken to respond may be a useful auxiliary measure.
Bias risk Low
Operators may be reluctant to admit they are getting into difficulties, if they suspect that they, not the system, are on trial.
Ethical problems None
None, provided it is made clear, before any simulation, that information on the performance or physical state of individual controllers will not be disclosed or quoted in any identifiable form.
Costs of the method
Staff Cost Nil
Distribution and collection of MCH forms can be handled by simulation staff.
Set-up Cost Low
Since all briefing material and recording forms are publicly available, set-up cost is very low. The test must be properly explained, in addition to the printed explanations, by someone of sufficient status to convince the controllers that it is to be taken seriously.
Running Cost Low
The only running cost is that of one form per controller per exercise.
Analysis Cost Low
Analysis may requires the transcription of the controllers’ responses, although these could be collected automatically.
Analysis data
Analysis Speed Fast
In principle, results should be available immediately minutes after the exercise.
Data Automation Easy
A simple data collection program could be incorporated into the simulator software. To date, there has been no pressure for this to be done.
Analysis Automation Easy
Easily implemented on a palm-top or laptop computer.
Status Established
Established - routinely used.

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