[摘要] 1. This report concerns on the yielding efficiency of variety test of sweet potato cultivated in all prefectural Agricultural Experiment Stations of Japan from 1939 to 1948, the cases investigated amount to 7500. 2. The distribution of per tan yield of sweet potato root tuber occupys 50-1600 Kan, and the Mo. 675 Kan, M. 632 Kan, σ 225 Kan, and the curve shows a beautiful monomodal symmetrical distribution. 3. The mean per tan yield of sweet potato tuber is about 630 Kan and displays no difference in both the northern and southern regions of Japan. 4. The distribution of per tan yield of sweet potato vine occupys 50-1700 Kan, and the Mo. 450 Kan, M. 553 Kan, σ 282 Kan, and the curve shows a monomodal asymmetric distribution, and its center of gravity inclines to the left. 5. the mean per ten yield of sweet potato vine is about 550 Kan and displays an increase in the north-eastern region and displays a decrease in southern region. 6. The distribution of sweet potato tuber percentage, that is, the ratio
occupys 10-500 %, and the Mo. 100%, M. 143%, σ 76.8 % and the curve shows a monomodal asymmetric distribution, and its center of gravity inclines to the left. 7. The mean sweet potato tuber percentage is 143 % and displays an increase in the south-western region and displays a decrease in the northern region. 8. The auther compared the sweet potato yield with the rice yield according to Calorie calculation. The minimum, mean and maximum Calorie of the per tan yield is respectively 500, 000-1, 500, 000-2, 500, 000 in rice, and in sweet potato 500, 000-3, 000, 000-6, 500, 000.
