h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

It is a basic principle in the world of measurement that the method used to determine the value of some parameter should not significantly influence that value. In other words, the value of the parameter should, to all intents and purposes, remain unchanged whether we measure it or not. The parameter of interest might be a physical thing, like the distance between two points, or the pressure in a pump or the speed of a particle in the Large Hadron Collider. For items such as these, many years of experiment and practical experience tell us how to make such measurements benignly.

No reputable laboratory would permit the measurement method to become so intrusive that the original value is completely distorted to the point where the 'measured value' is determined entirely by the measurement method. However every day we, the General Public, permit such measurement distortions to be portrayed as fact. Take for example, waiting times at hospital Accident and Emergency departments. The government's target time to attend to a self-transported patient is within 4 hours. All well and good; we'd all like the waiting time to be a lot lower, but better service costs more money. In reality the method of attending to patients is now driven by this target time. Once a patient has been logged into the system by the receptionist, the clock is up and running, but if the patient has been initially assessed by the medical staff, and is now lying in an assessment unit (or worse a corridor), waiting for something or somebody else, then the clock stops. The patient has been seen within the required time, a tick is in the box and the statistics are satisfied. But the measurement of the performance of the A&E department as regards the service received by the patient has been completely lost and destroyed by the method used to determine it.

Another example of such measurement distortion came to light this week with the disruption caused by the snow and ice. Many schools are closed, causing difficulties for parents. What is the principal reason why schools are closed? Teaching staff not able to make it to school? Broken-down heating systems? Health and Safety issues in classroms? Or could it be that when schools are closed, the attendance figures do not count towards a school's attendance target figures, whereas if they open they do.

Tail wagging the dog has got nothing on the effect of government 'targets'.