One of the advantages of having monitoring programmes is that data from many laboratories are available to support trouble shooting. For example, if only one laboratory reports a particular problem and it is not seen in any other laboratory one might conclude that the problem lies within that laboratory. If several laboratories all have a similar problem using the same batch of the same test one might conclude that the problem lies with the test or with a batch of that test. This can save a lot of effort and money in a testing system.