## 3 Experiment
### Data Pre-Processing  
The dataset consists of four signal channels associated with EDA, body temperature (Temp.), BVP and HR. EDA is collected from electrodermal activity sensor measured in \(\mu\)S with frequency of 4 Hz. Body temperature data are measured on the Celsius (\({}^{\circ}\)C) scale with a frequency of 4 Hz [15]. BVP data are from photoplethysmograph (PPG) and sampled at 64 Hz [15]. HR data are the average heart rate values per second, derived directly from the BVP analysis [16]. All the signals were downsampled to 1 Hz for data analyses. The data are associated with ten participants, each participant has four sailing sections, the data can be split into forty samples (see Table 1). In order to compare the data with different resolutions, and to make it easier to analyse, we have normalized the downsampled data.  
Figure 4: Comparison of the NASA-TLX rating results for students, experts and overall. The number from 1 to 6 presents Mental Demand, Physical Demand, Temporal Demand, Performance, Effort, and Frustration Level, respectively.  
Figure 3: Comparison of the NASA-TLX rating raw score for students, experts.  
Normalization of the data is done by calculating the standard normal distribution. The standard normal distribution is the simplest case of the normal distribution when the data are standardized to have a mean of zero and a standard deviation of one [17]. Before calculating the standard normal distribution, the standardized value of the signal data is computed from the mean and standard deviation using the following formula (see Equation (1)) [18]:  
\[z_{i}=\frac{x_{i}-\bar{x}}{S},\ \ \ \ \ i=1,2,\ldots,n \tag{1}\]  
where \(z_{i}=\{z_{1},z_{2},\ldots,z_{n}\}\) is standardization value of the sample, \(x_{i}=\{x_{1},x_{2},\ldots,x_{n}\}\) is the value of the downsampled signals, \(\bar{x}\) is the mean of \(x_{i}\) on each file, \(S\) is the sample standard deviation, \(n\) is the number of the data on each file.  
Finally, the standard normal distribution of the data was calculated using Equation (2) [19]:  
\[f(z_{i})=\frac{1}{\sqrt{2\pi}}e^{-\frac{z_{i}^{2}}{2}},\ \ \ \ \ i=1,2,\ldots,n \tag{2}\]  
\begin{table}
\begin{tabular}{p{11.4 pt} p{11.4 pt} p{11.4 pt} p{11.4 pt} p{11.4 pt} p{11.4 pt} p{11.4 pt}} \hline \hline
**No. of Samples** & **No. of Participants** & **No. of Sailing Sections** & **Signal Sailing Sections** & **Signal Channel** & **Signal Channel** & **Signal Channel** \\ \hline Sample & & Sailing section & EDA data & Temp. data & BVP data & HR data \\ \hline Sample & & Sailing section &.. &.. &.. &.. &.. \\ \multirow{2}{*}{Participant 1} & Sailing section &.. &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. &.. \\ \multirow{2}{*}{.} & Sailing section &.. &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. &.. \\ \multirow{2}{*}{.} & Sailing section &.. &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. &.. \\ \multirow{2}{*}{.} & Sailing section &.. &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. \\ \multirow{2}{*}{Participant 10} & Sailing section &.. &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. \\  & & Sailing section &.. &.. &.. &.. \\ \multirow{2}{*}{Sample 40} & Sailing section & & & & & \\  & Sailing section &.. &.. &.. &.. &.. \\ \multirow{2}{*}{Sample 40} & Sailing section & & & & & \\where \(z_{i}=\{z_{1},z_{2},\ldots,z_{n}\}\) is standardization value of the sample and \(n\) is the number of the data.  
All 40 samples were labelled into two categories: expert and novice.