What are homogeneity and generalisability?

People with the same disease may have symptoms in common, but they do not have identical symptoms, and they do not have identical responses. In setting up trials for orthodox drug treatments, this diversity has to be taken into account, but it creates conflicting demands:For the drug to be shown to be effective for a known set of symptoms, the cases used in the trial must be as similar as possible (the group must be homogeneous), but a completely homogeneous group is impossible to find;For the drug to have a general applicability for all those suffering the disease, the widest possible range of cases need to be included (the group needs to be general), but this increases variability in the responses and reduces the scientific value of the results.

There are several consequence of these conflicting demands:There can be no such thing as a perfect trial, since trials inevitably involve a compromise between homogeneity and generalisability.The results are only more or less scientific and only more or less applicable to people suffering the disease. [1]Scientific accuracy may often be sacrificed for financial reasons. [2]The individuality of response in patients means that drugs produce side effects, and these may not be identified during the trial.
As a result orthodox medicine recognises that controlled trial evidence alone cannot be relied on, but must be compared with evidence from clinical practice, a approach which forms the basis of evidence based medicine (EBM).

The only real scientific solution to this problem is to test potential treatments on healthy people in order to identify all their actual effects on individuals (aswhich is what homeopaths do in provings), and then have a method of systematically relating this information about effects to the individual needs of patients which is what homeopaths do when selecting a remedy).

References
1. Harris L Coulter, The Controlled Clinical Trial: An analysis (Washington (DC): Center for Empirical Medicine Project Cure, 1991), pp. 29-44
1. Harris L Coulter, Homoeopathic Science and Modern Medicine (Berkeley: North Atlantic Books, 1981), pp. 163-167.

Related pages:
Why it worksGeneticsIndividualisationProvings
Orthodox medicineWhat are diseases?What is effectiveness?What is evidence?What is evidence based medicine (EBM)?What are side effects?