This article is a continuation of a previous article in World Patent Information, Vol. 8 No. 2, pp. 122-142, which described the basis of a statistical theory of the development of a technical field. It presents a detailed verification of the possibility of failure of the theory through not describing the development of patent activity with sufficient accuracy. The analysis is based on the simplest model of the theory and discusses in detail: 1. 1. Analysis of activity in the field of coil dialyzers.2. 2. Analysis of Edison's patents.3. 3. Application of the theory to several examples published in World Patent Information.4. 4. Analysis of citations. The main conclusions are that the simple model of the theory is relatively accurate for fields of small extent but for large fields, or those comprising several sub- fields, the simple model is not satisfactory. For extensive files the simplest model can be used to provide a rough estimate of trend of development.