ABSTRACT
When the statistical analysis described in Chapter 6 indicates that a direct method of measurement cannot produce valid or reproducible observations, due to too great variability in the conditions or materials involved in measurement, we have then to study methods of indirect measurement. Assays of many biochemical substances are of this type. Similar types of problem arise if different methods of measurement are used in different clinics or if there is a proposal to replace an established method by some cheaper or more efficient alternative method.
