*3.3.3 No underlying pattern on occurrences of Eij given i*

Each individual is independent of the others. As a result, *the number of events and the instant* at which they occur may differ from individual to individual without any underlying pattern.

*There is no agreement among psychiatrists about the quantity of ES that must be applied to a given patient.*

If a common pattern of occurrences *E* overtime, **Figure 4**, had been present in this domain for all individuals, then it would have been feasible to consider and analyze a single series per individual using, for example, an *intervention policy* [14] characteristic of statistical time series models, therefore, as our particular domain does not conform to this prior assumption it is not appropriate to use a classical temporal analysis.

*For example, the Electroconvulsive Therapy (ECT) applied to a patient consists of a variable number of sessions depending on the patient's condition, and their distribution over time is decided according to medical criteria for each particular case (between 6 and 12 ES per therapy). The frequency of ES may not be constant throughout the therapy (it is usual to increase the time between sessions as the patient improves. Normally be 2 or 3 ES per week).*

Therefore, it is necessary to keep the series *ni* distinguishable for each individual.

**Figure 4.** *Common pattern of occurrences* E *over time.*

*Toward Optimization of Medical Therapies with a Little Help from Knowledge Management DOI: http://dx.doi.org/10.5772/intechopen.101987*

### *3.3.4 Too small series*

Derived from the above, the *ni* series non-independent per individual must be treated separately, and no summary series will be constructed. Since the number of observations in each series is too small, and estimation of the time series model becomes impossible, as the number of parameters is larger than the number of observations. Therefore, a classical time series analysis is not the right approach for this problem. Consequently, KDSM formally works every *Y<sup>t</sup> ij t* ¼ f g 1 … *r* given *Eij* and *r* is too small.
