## 3 Results and Discussion
The reason is standard deviations of both results for three-fold cross-validation are 0.1%, and 0.2%, while their accuracy values are 78.7% and 83.3%, respectively. Hence, all three-fold results were consistent with just small differences. In Figure 5, because N-N and A-A pair distributions were well separated into separate quadrants of the feature space, our expectation was the normal-abnormal pair values distributed to the other quadrants. For example, in Figure 5a, N-N pairs both right and left values less than 0, A-A pairs values greater than \(-\)0.5, and A-N (ear pair right side abnormal and left side normal) pairs (represented with a black circle) supposed to distribute lower-right quadrant of the figure. Likewise, for N-A (ear pair right side normal and left side abnormal) pairs (represented with blue circle) are supposed to distribute the upper-left quadrant of Figure 5a. However, black and blue circles mixed in N-N and A-A pair values are presented in Figure 5a,b. This caused a decrease in the accuracies for transfer learning test results and lookup table based feature extraction system results after adding normal-abnormal pair images. After we observed these unexpected distributions of blue (i.e., N-A) and black circles (i.e., A-N), our ENT expert examined the normal-abnormal pair images, which were selected from video frames of both adult and pediatric patients' tooscope video clip. He labeled the normal-abnormal pair images as'subtle' or 'not subtle', and 63.3% (19/30) of the pair images were labeled as'subtle'. Figure 6 illustrates four examples of pair images that were labeled as'subtle' by our ENT specialist and misclassified by transfer learning. Figure 4: Results of Three-Fold Classification Accuracies for Different Feature Vectors Only Normal-Normal and Abnormal Pairs and after added Abnormal-Normal/Normal-Abnormal Pairs. Imaging problems may be the reason for misclassification. Three pairs had illumination problems that manifest themselves on images as yellow or white light spots, which makes it difficult for the camera to focus on the eardrum region. Another common problem was ear wax and hairs, because they were closer than the eardrum to the otoscope, reflecting light. Furthermore, the eardrum region of the image was not enough to classify its category. The blurry parts of the images were another problem with these images. The second column of Figure 6 demonstrates images with out of focus problems. While Figure 6c-Normal is an in-focus image, Figure 6c-Effusion is blurry between the two regions with light reflections. In contrast, Figure 6d-Effusion and d-Normal contain blurry regions, regardless of the amount of light reflection. The accuracy of the system will likely decrease, depending on the problems (light, wax, hair, or blurring) of the normal-abnormal pairs' images. However, it should be noted that  
Figure 5: Lookup value distribution of Right and Left side of eardrum for Normal-Normal, Abnormal-Abnormal, Normal-Abnormal, and Abnormal-Normal pairs. While Normal-Normal pairs first lookup table values located in the lower-left corner and Abnormal-Abnormal pairs first lookup table values located in the upper-right corner of (**a**), and vice versa for (**b**). The first values of right and left normal pairs (N-N) were less than zero, and for abnormal pairs (A-A), the same values were greater than \(-0.5\) (**a**). For the second lookup table values, N-N and A-A pair corners switched (**b**). Our expectation was Normal-Abnormal pairs would state on the upper-left, and Abnormal-Normal pairs would state on the lower-right corner of (**a**), and vice versa for (**b**). However, Normal-Abnormal and Abnormal-Normal pairs stated mixed into other pairs. The number of Normal-Abnormal and Abnormal-Normal pairs are very limited, and most of them are subtle. Figure 6: Examples of pair misclassified eardrum images labeled as subtle. Images are shown with the left ear on the right and right ear on the left.