Repeatability and number of measurements for productive variables in vegetable crops experiments

ABSTRACT One of the ways to optimize the evaluation of the experiment and obtain high precision of the results is with the use of an adequate number of measurements for each variable observed in the experiment. In this sense, the objective of this study was to estimate the repeatability coefficient and the number of measurements necessary for the analysis of characters of production of zucchini, cucumber, pout pepper and pea. In the experiments carried out with zucchini and cucumber the variables number of fruits, fruit mass, fruit length, largest fruit diameter and smallest fruit diameter were evaluated. For pea the number, length and mass of pods, number and mass of grains per pod and for pout pepper number and mass of fruits, largest fruit diameter and length were evaluated. The repeatability coefficient (r) was estimated by the principal component method using the correlation matrix and the covariance matrix. The number of measurements for each variable was also determined based on the coefficients of determination of 0.80, 0.85, 0.90, 0.95 and 1.00. The estimated repeatability coefficient obtained the highest estimates using the covariance matrix, ranging from 0.67 to 0.84 for zucchini, from 0.66 to 0.97 for cucumber, from 0.47 to 0.70 for pea and from 0.57 to 0.71 for pout pepper. To evaluate the fruit mass in zucchini, cucumber, pea and pout pepper, are exactly, respectively, 7, 4, 8 and 8 measurements for a coefficient of determination of 95%.摘要 优化实验评价流程并获得高精度实验结果的有效途径之一，是为实验中观测的每个变量配置合理的测量次数。有鉴于此，本研究旨在估算西葫芦（zucchini）、黄瓜（cucumber）、皱皮椒（pout pepper）与豌豆（pea）的产量性状分析所需的重复系数（repeatability coefficient）与最优测量次数。 针对西葫芦与黄瓜的实验，本研究评估了单果数、单果质量、果实长度、最大果径与最小果径5项变量；针对豌豆的实验，评估了荚果数、荚果长度、荚果质量、单荚粒数与单荚粒质量；针对皱皮椒的实验，则评估了单果数、单果质量、最大果径与果实长度。 本研究采用基于相关矩阵（correlation matrix）与协方差矩阵（covariance matrix）的主成分分析法（principal component method）估算重复系数，同时基于0.80、0.85、0.90、0.95与1.00的决定系数（coefficient of determination）水平，确定了各变量所需的测量次数。 基于协方差矩阵估算得到的重复系数结果最高：西葫芦的重复系数区间为0.67~0.84，黄瓜为0.66~0.97，豌豆为0.47~0.70，皱皮椒为0.57~0.71。当决定系数为95%时，西葫芦、黄瓜、豌豆与皱皮椒的果实质量评估所需的测量次数分别为7次、4次、8次与8次。