As we use the median method to find the class that most reflects a centralising tendency, similarly we can use the Severity rating in the same way. This method has no official recognition. If you use it don’t record it on any template. Rather than just using the severity rating for the median class, use it for each class.
For example
Intelligence 1 L
Thinking 2 M
Perception 2 L
Judgment 2 M
Mood 3 L
Behaviour 2 H
Determine the median class, here Class 2 (the middle number).
Then determine the median severity of all the classes in the median class. .For severity ranges in classes outside the Median Class, the rule is to adjust ratings in any class below the Median Class to the Low range in the Median Class and for any ratings in classes higher than the Median Class to the High range in the Median Class.
! L 2 M 2 L 2 M 3 L 2 H becomes L M L M H H
In order = L L M M H H, the median severity in Class 2 is M
Percentages for Range of Severity
| Classes | 1 | 2 | 3 | 4 | 5 |
| Low | 0-1% | 10-12% | 25-30% | 55-60% | 75-80% |
| Medium | 2-3% | 14-16% | 35-40% | 65-70% | 85-90% |
| High | 4-5% | 18-20% | 45-50% | 70-75% | 95-100% |
The WPI impairment is then between 14-16%.
If there is no clear median eg L L L M M H where the 2 middle letters are L and M, then the WPI is a percentage between these 2 ranges, in the example above if the severity ratings in order were L L M H H H, the final WPI is between the range for medium and the range for high, I,e, 16-18%. The final figure is for you to decide.
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