# Exploration of Machine Learning Models for Prediction of Gene Electrotransfer Treatment Outcomes
## 3 Results
### \(\chi^{2}\) Results for Feature Selection  
The results of the \(\chi^{2}\) test are provided in Figure 2. The highest-ranked features were pulse voltage and pulse width, which means that these variables were most highly correlated with the outcome variable, either the'success' or 'failure' of the treatment. Scores are given as \(-\)log(\(p\)), where \(p\) is the \(p\)-value of the corresponding \(\chi^{2}\) test between the individual feature and the outcome of the experiments. Scores greater than 1 were considered to significantly contribute to the prediction of the outcome variable [57]. The  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Source** & **Plasmid Common Name** & **Species/Cell Line** & **Electrode** & **Pulse Polarity** & **Experiments** \\ \hline [51] & pVEGF & Sprague Dawley Rat & 4-Plate & Positive & 2 \\ \hline [52] & gWiz-Luc & C57B1/6 Mouse & Caliper + 6-Needle & Positive & 8 \\ \hline [22] & pUMVc3-hIL-12-NGLV3 & Human & 6-Needle Circle & Positive & 24 \\ \hline [53] & pEGFP-C1 & Chinese Hamster Ovarian Cells & 4-Pin Circle & \
\begin{tabular}{c} Positive + \\ Alternating \\ \end{tabular} & 4 \\ \hline [54] & phGFP-S65 ST & C57 Black/C Mouse & 2-Plate & Alternating & 1 \\ \hline [54] & phGFP-S65 ST & Wistar Rat & 2-Plate & Alternating & 1 \\ \hline [26] & gWiz-Luc & HaCaT Cells & Cuvette & Positive & 2 \\ \hline [44] & pCMV-dTomato & C57B1/6 Mouse & Contact Wire & Positive & 9 \\ \hline [11] & pDRIVE2-CMV & Mesenchymal Stem Cells & Cuvette & Positive & 7 \\ \hline [55] & pVAX2-LUC & C57 BL/6 Mouse & Plate + 7-Pin Hex & Positive & 3 \\ \hline [56] & pVax1-hVEGF165(pVEGF-A) & Yorkshire Pig & 4-Pin & Positive & 1 \\ \hline [3] & pCH110 & Wistar Rat & 2-Pin & Positive & 4 \\ \hline [45] & gWiz-Luc and NTC9385R-Luc & Sprague Dawley Rat & Monopolar + 4-Pin &
\begin{tabular}{c} Positive + \\ Alternating \\ \end{tabular} & 4 \\ \hline [5] & gWiz-Luc and NTC9385R-Luc & Sprague Dawley Rat & Caliper & Alternating & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._  
Figure 1: Magnitude of the electric field (\(\left|\overrightarrow{E}\right|\)) in cardiac muscle directly below the 1 cm\({}^{2}\) platinum electrode during 100 ms pulse of 90 V. Max field is fringe field at 45 V/cm with bulk field at 25 V/cm.  
differences between subsequent scores decreased after the highest four scores, so those scores were always included as part of the limited predictor dataset.  
The bootstrapped rankings of 100 resamplings are shown in Figure 3. While several predictors changed relative ranks compared to the single-sample \(\chi^{2}\) testing described in Figure 2, the top four predictors remained the same, making them robust to the resampling of the data.  
Figure 3: After 100 resamplings, pulse voltage and pulse width remained highly ranked features. The bars represent 95% confidence intervals for the mean (\(\bullet\)). A rank of 1 corresponds to the best predictor, whereas a rank of 24 corresponds to the worst predictor.  
Figure 2: Pulse voltage and width were variables most highly correlated with the outcome variable. Scores from \(\chi^{2}\) testing between individual features and significance variable. Scores are ranked from high (left) to low (right) in order of relation to the true outcomes of each experiment. This figure is the result of one set of \(\chi^{2}\) tests.