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When the diameter breast high is measured with the callipers, the following errors are anticipated. (1) The error owing to the direction of measurement. (2) The error owing to the height of measuremen...t. (3) The error owing to the angle between the callipers and the stem axis. (4) The error owing to the angle between two arms of the callipers. Since (4) is a constant error, only (1) (2) and (3) are to be treated. The first report treats only (1), especially the random sampling method in the measurement of diameter breast high. As the method of diameter breast high measurement, we used to measure the maximum and minimum diameters purposefully. Against this, the method of measuring the diameter at random is considered. The first problem with the random sampling method is what indicates the estimate value by the random sampling method. The answer is the average diameter of all direct diameters of about all trees as expressed by Equation (1). Unless the sectional form is circular, the estimated diameter is not identical with the true diameter. The bias is expressed by Equation (4). The bias is negligibly small with the practical data. Under the assumption that the sectional form is elliptical, the bias with one tree is shown in Table 1 and the difference between the theoretical bias and practical bias is shown in Table 2. As given in table 2, the practical bias is larger than the theoretical bias by 1.4 times. Using the random sampling method, the variance increases because the sampling variance is added. The increase of variance is expressed by the second term in the right hand of Equation (5). Inserting the practical data in this equation, the increase of variance by random sampling method is 0.8 per cent. After all, the random sampling method is better than the purposive method for the practical use, because the bias is negligibly small, the increase of variance is within 1 per cent and because the frequency of measurements is reduced about by half.続きを見る
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I 緒言 II 試料 III 任意抽出法の妥当性について 1 理論的証明 2 試料に基づく実際的証明 IIII 任意抽出法による変動の増加について V 任意抽出法と有意抽出法との比較 参考文献
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Mendeley出力
KJ00005469777