## 4 Discussion
### Impact of Variability on Assessment  
As shown in Table 2, the chronological age of the participants for whom both the therapist and prosody expert evaluations were available was similar. However, their skills for reasoning, recalling auditory verbal material and understanding vocabulary were clearly different. Given the sample selection criterion (see Section 2.2), the heterogeneity found in these developmental measurements was expected. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **CA** & **VA** & **NVCL** & **MPercT** & **MProdT** & **RRate** & **ContRRate** & **ContRate** & **RepRate** & **CR** \\ \hline CA & 1.0 & \(-\)0.29 & \(-\)0.36 & \(-\)0.53 & \(-\)0.49 & \(-\)0.64 & \(-\)0.52 & 0.53 & 0.5 & \(-\)0.16 \\ VA & & 1.0 & **0.96** & **0.93** & 0.84 & **0.91** & **0.97** & \(-\)**0.91** & \(-\)**0.96** & 0.42 \\ NVCL & & & 1.0 & 0.87 & 0.76 & **0.9** & **0.95** & \(-\)**0.92** & \(-\)**0.93** & 0.29 \\ MPercT & & & 1.0 & 0.83 & **0.98** & **0.96** & \(-\)0.86 & \(-\)**0.99** & 0.36 \\ MProdT & & & & 1.0 & 0.81 & **0.89** & \(-\)**0.93** & \(-\)0.83 & 0.80 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Correlation values (Pearson correlation coefficient) between C1 speakers’ profile variables (Table 2) and evaluators’ assessment (Table 5). RRate means the percentage of Right judgments of the prosody expert. ContRRate, ContRate and RepRate mean the percentage of Cont.R, Cont. and Rep. evaluated by the therapist, respectively. CR means the classification rate of the SVM classifier. Values in bold represent statistically significant correlations with \(p\)-value \(<\) 0.05. As shown in Table 6, when the developmental level is low, the quality of the prosodic productions is also low (positive high correlation with the VA-RRate and the VA-ContRRate and negative high correlation with the VA-ContRate and the VA-RepRate). This has an impact on the raters' assessment and on the likelihood of their agreement as to the appropriateness of the output. The speakers S01, S02 and S03--who had the highest developmental and prosodic level (Table 2)--present higher values of agreement in right cases (R-Cont.R) than the S04 and S05 speakers (Table 5). This shows the difficulties inherent to the task being carried out. Furthermore, even in the cases of a higher cognitive level, variability in the linguistic profile can also play a role. Thus, levels of vocabulary are not necessarily paired with those of prosody perception and production (Table 2). A high prosodic perception level seems to help players to obtain a better assessment in their speech productions (positive highly correlated MPercT-RRate, MPercT-ContTRate; negative highly correlated MPercT-RepRate). A high prosodic production level seems to be related to a good assessment of the recordings, but the correlation is only significant with ContRRate and ContRate (Table 6). The lack of statistical significance in other high correlation coefficients (e.g., MPercT-ContRate) can be explained by considering the small sample size. In short, agreement between the prosodic expert and the therapist depends on the speaker's developmental levels and the type of sentence produced (right or wrong). In addition, differences in the evaluation context can also explain raters' disagreements. Thus, while the expert only based her decisions on intonational criteria, the therapist also took into consideration the progress of the player while playing the video game. In doing so, avoiding frustration was a priority; therefore, levels of frustration tolerance and number of failures influenced the therapist's decisions. The high variability of the speech of individuals with Down syndrome has also been shown in our experimental results regarding the use of prosodic features. Table 4 shows the differences in the correlated features with the expert evaluation per speaker. Some rhythm and frequency features appear above in the ranking of all the speakers (from _silencesMean_ to _F0 semitoneFrom27.5 Hz_sma3 nz_stddevFallingSlope_ on Table 4).