## 3 Results  
To verify the results of the algorithm implemented in the application, a generic medical-grade pulse meter was used to obtain the reference readings, which will serve as a comparison with our results. In this study, two measurements were made on each of the 47 subjects. Some of the values of the test blocks made and obtained using our application and using the medical pulse-oximeter are shown in Table 1.  
Through an ongoing process of acquisition and comparison--with respect to the medical pulse-oximeter (reference device)--our application showed an error rate of approximately 3% to 5%, as shown in Table 2. Error calculation was performed by obtaining the absolute error and the relative error. The population investigated included 47 healthy volunteer subjects, with an age range between 18 and 22 years, in an environment with artificial lighting, at rest in a chair.  
Figure 7 shows a graphical representation of the relationship between the two methods, between the readings of our application and the readings of the pulse-oximeter. This figure shows the heart rate accuracy of our application and where the margin of error is acceptable.  
\begin{table}
\begin{tabular}{c c} \hline
**Reference PPM** & **Application Estimated PPM** \\ \hline
67 & 65 \\
70 & 70 \\
82 & 83 \\
84 & 85 \\
87 & 88 \\
88 & 90 \\
100 & 99 \\
106 & 104 \\
108 & 107 \\
111 & 110 \\ \hline \end{tabular}
\end{table}
Table 1: Pulses per minute (PPM) values obtained (less 20%) in different subjects during the validation process.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Descriptive Statistics** & & & & \\ \hline
**Variable** & **Count** & **Mean** & **Standard Deviation** & **95\% LCL of Mean** & **95\% UCL of Mean** \\ \hline POX reference device & 47 & 89.40 & 13.9 & 85.4 & 93.38 \\ App PPM & 47 & 89.04 & 14.4 & 84.9 & 93.2 \\ Correlation Coefficient & & 0.97898971 & & & \\ \hline \end{tabular}
\end{table}
Table 2: Descriptive statistics between the two methods and their correlation coefficients.  
The Bland-Altman method was used as a graphic method to compare the two measurement techniques acquired from the same quantitative variable (in the present investigation, this variable is heart rate). This method measures the difference between the acquisition method of a medical pulse-oximeter compared to our application. Figure 8 shows the graph with the Bland-Altman method to quantify the average between both methods, obtaining more than 95% reliability in the data obtained, thereby verifying the variability and precision of the techniques.  
The average of the two measurements is plotted along the horizontal axis, and the difference between the two methods is plotted along the vertical axis.  
Figure 8: Bland–Altman plot between the reference values and the values obtained by our application.  
Figure 7: Relationship between the two methods, the reference values, and the values obtained by our application.  
We can observe in Figure 8, through a visual impression of the Bland-Altman graph, that the data obtained by our application, in comparison to the reference device, have high precision. Most of the data are within the agreed limits, thus validating the certainty and precision of the technique used.  
Table 2 describes the statistical study made between the two methods and shows a report of the basic descriptive statistics and confidence intervals for the two variables and their differences.  
As seen in Table 2, the correlation coefficient is 0.97, which illustrates that our application has a perfect positive linear association with the comparison device. Based on this index, our application has an error rate of approximately 3 to 5%, as described in the results section.