## 4 Discussion  
This paper is written from a design and engineering point of view, where existing anthropometric data were used in order to prove canons that could later be used for establishing potential anthropological-biomechanical models and ensure more effective children's product design. The data of head length (HL) to total body height (BH) for this article were extracted from two dissertations of authors who deal with furniture design in educational institutions. The research presented in this paper began with the aim of determining potential head-body canons, and does not present statistical data related to precise anthropometric or medical research. A canon is considered as a set of rules and principles for body proportions as it was set throughout art history. An artistic canon of body proportions (or aesthetic canon of proportion), in the sphere of visual arts, is a formally codified set of criteria deemed mandatory for a particular artistic style of figurative art. Therefore, the goal of this work was to determine a potential canon for children with our available data and highlight the need of future interdisciplinary research. Figure 3: Ratios regarding gender per age group. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Age Group** & **Gender** & **N** & **Mean (SD)** & \
\begin{tabular}{c} **95\% CI for** \\ **the Mean** \\ \end{tabular} & **Median** &
\begin{tabular}{c} **95\% CI for** \\ **Median** \\ \end{tabular} & **Min-Max** & **Skewness** & \(p\)***** \\ \hline \multirow{2}{*}{\(\geq\)11\(\sim\)12} & Male & 36 & 6.96 (0.46) & 6.80–7.11 & 6.97 & 6.76–7.18 & 6.00–8.05 & 0.059 & \multirow{2}{*}{0.02} \\  & Female & 38 & 7.22 (0.44) & 7.07–7.36 & 7.19 & 7.04–7.41 & 6.22–8.32 & 0.189 & \\ \hline \multirow{2}{*}{\(\geq\)12\(\sim\)13} & Male & 37 & 7.39 (0.67) & 7.16–7.61 & 7.22 & 7.00–7.56 & 6.32–8.95 & 0.574 & \multirow{2}{*}{0.44} \\  & Female & 29 & 7.50 (0.53) & 7.30–7.70 & 7.46 & 7.18–7.78 & 6.64–8.62 & 0.420 & \\ \hline \multirow{2}{*}{\(\geq\)13\(\sim\)14} & Male & 34 & 7.45 (0.45) & 7.30–7.61 & 7.42 & 7.23–7.69 & 6.60–8.29 & 0.002 & \multirow{2}{*}{0.47} \\  & Female & 36 & 7.53 (0.41) & 7.39–7.67 & 7.46 & 7.30–7.64 & 6.59–8.60 & 0.473 & \\ \hline \multirow{2}{*}{14\(\sim\)15} & Male & 38 & 7.58 (0.51) & 7.41–7.75 & 7.50 & 7.40–7.77 & 6.76–8.79 & 0.321 & \multirow{2}{*}{0.40} \\  & Female & 24 & 7.69 (0.53) & 7.47–7.92 & 7.60 & 7.42–7.87 & 6.83–8.90 & 0.748 & \\ \hline \hline \end{tabular}  
* Student’s \(t\) test; \(t\) reject normality (Kolmogorov–Smirnov test).  
\end{table} 
Table 5: _Cont._Considering the previously mentioned researchers of artists and engineers throughout the centuries, it is confirmed that the canons between 5.5 HL and 7.5 HL for children of kindergarten and primary school age are still valid today. It is interesting to note how children's canons, although they move within the observed ratios (5.5 HL to 7.5 HL), have increased over time with regard to the observed age of the children. The made comparison of the canon (Table 6) shows that, for example, according to [25], the canon for children between 4 and 5 years is 5.5, while the new research shows the average value of boys and girls from Table 5 and is 5.99 HL. A similar thing can be seen when comparing, for example, [5] and the results presented in this paper for children 4-5, 10-11, and 14-15 years old. This leads to the conclusion that children of the same age have grown over the last 100 years, which is in line with secular trends (changes in the growth and development of children) confirmed by researchers around the world [15; 16; 33]. (Table 6)  
In addition to the canon of head length (HL) to body height (BH), many researchers observe other body dimensions and proportions in correlation with anthropometry [34], as well as socioeconomic factors [35; 36], beauty, growth, and health [37; 38], furniture [39], clothes [40], clinical, or nutrition standards [41; 42; 43].