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Item Response Theory (IRT) evaluates, on the same scale, examinees who take different tests. It requires the linkage of examinees’ ability scores as estimated from different tests. However, the IRT linkage techniques assume independently random sampling of examinees’ abilities from a standard normal distribution. Because of this assumption, the linkage not only requires much labor to design, but it also has no guarantee of optimality. To resolve that shortcoming, this study proposes a novel IRT based on deep learning, Deep-IRT, which requires no assumption of randomly sampled examinees’ abilities from a distribution. Experiment results demonstrate that Deep-IRT estimates examinees’ abilities more accurately than the traditional IRT does. Moreover, Deep-IRT can express actual examinees’ ability distributions flexibly, not merely following the standard normal distribution assumed for traditional IRT. Furthermore, the results show that Deep-IRT more accurately predicts examinee responses to unknown items from the examinee’s own past response histories than IRT does.

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The approximate surface development, skin length, and surface area of the left side of the trunk of 51 female students were compared with regard to static and stretched postures. The data for each subject were obtained from geometrical models generated by moiré topography with a computer. When the chest was stretched, the anterior surface, the shoulder line, and the arm-base line were transformed from concave to convex, and a gap oriented toward the nipple widened out. The skin elongated vertically and transversely, except at the side of the waistline, where the skin contracted. The area at the top of the trunk decreased about 25%, while the other parts of the trunk increased 8-15%. The total anterior area was 1.20 m2 for the static posture and 1.29 m2 for the stretched posture. When the posterior surface was stretched, the shoulder line changed from convex to concave, the side line from quasi-straight to concave, and gaps oriented toward the chest line disappeared. The skin elongated most at the infrascapular region (20-35%), while the neck base line contracted (-11%). The center of the back and the lower arm base areas enlarged the most (25%) and the lumbar area enlarged the least (12%). The total posterior area was 1.26 m2 in the static posture and 1.37 m2 in the back-stretched posture. In conclusion, the back skin elongated and enlarged more when stretched than the frontal skin.