## 4 Discussion

Table 6: Test statistics and confidence intervals regarding the support vector machine classification using a quadratic kernel. amplification, (iii) open-set sentence scores in quiet in the worse ear <65% and in the better ear <85%, (iv) open-set phoneme scores in quiet in the worse ear <45% and in the better ear <65% with no radiological or medical contraindications, (v) appropriate expectations and commitment from client and family, and (vi) motivation of the client [29]. The most recent practice policy for cochlear implantation of the American Speech-Language-Hearing Association (ASHA) was published in 2004 [30]. This policy permits cochlear implantation in subjects 2 years and older if pure tone average thresholds are at 70 dB HL or greater, and in children younger than 2 years of pure tone average thresholds are at 90 dB HL or greater. For adults, cochlear implantation is permitted for open-set sentence recognition scores of up to approximately 50 to 60%. A question central to the indication of cochlear implantation is \"Is it likely that an individual will receive more communication benefit from a CI than from a hearing aid or, alternatively, from no hearing prosthesis at all?\" [30]. Moreover, commercial manufacturers such as MED-EL and Cochlear Ltd. provide criteria for indicating cochlear implantation [31; 32]. In the report by MED-EL, slightly diverging implantation criteria are listed for a few countries, i.e., Germany, the United Kingdom, France, (Western) Australia, the Kingdom of Saudi Arabia, and the Republic of Korea. Examples of threshold hearing levels eligible for cochlear implantation range up to 70 dB HL, which may mark the borderline between moderate and severe hearing loss. Cochlear Ltd. even indicates on their website cochlear implantation at low-frequency threshold hearing levels of up to 40 dB HL [31]. Besides hearing thresholds, also subjects' and families' preferences, motivation, commitment, appropriateness of expectation, and other psychological aspects as well as aspects of quality of life play a role, and assessment differs for adults and children. In particular, a patients' hearing must be assessed in a holistic way instead of only applying strict criteria, which may turn the decision for a significant subset of individuals of the candidacy population [33]. To address some of these factors, the 'costs' of acoustic amplification \(\lambda_{\text{amp}}\) and cochlear implantation \(\lambda_{\text{imp}}\) that we proposed to be included in the decision process may be adjusted. These cost factors may be understood as means for assessing the relative weightings of burdens, costs, and risks of using a hearing aid and or cochlear implantation. A similar strategy was proposed in a broader context to assess patient preferences on clinical interventions in the past [34]. We saw that thresholds of IHCL indicating cochlear implantation varied considerably when the penalty parameters were varied. An added value of the presented study over current practical guidelines arises from the synergy between the state-of-the-art modelling approaches that were combined for the purpose of comparing available hearing prostheses options in a personalized way. For example, one may want to predict in clinically doubtful scenarios whether hearing performance is likely to improve when a CI is used, and how large the risk of a performance decrease may be. To the best of the author's knowledge the presented study is the first that proposes such a modelling approach for the purpose of working towards a non-black box decision support system for the clinical care of hearing impairment. While a holistic understanding of a patient's situation is important, the proposed modelling approach may be seminal for future studies that aim at establishing a physiologically grounded decision support. Limitations of the study and suggestions for future work include the following: First, for the fitting of the CIs, only the insertion depth of the electrode was used as a fitting parameter, and only the CIS strategy was used.