Sample size in the estimation of correlation coefficients for corn hybrids in crops and accuracy levels

This study determined the sample size necessary for the estimation of the Pearson linear correlation coefficients for single, triple and double corn hybrids in crops and accuracy levels. In 361, 373 and 416 plants, respectively, of the single, triple and double hybrids of the 2008/2009 crop and, in 1,777, 1,693 and 1,720 plants, respectively, of the single, triple and double hybrids of the 2009/2010 crop, twelve traits were measured: plant height, ear insertion height, ear weight, number of grain rows per ear, ear length and diameter, cob weight and diameter, weight of hundred grains, number of grains per ear, grain length and grain yield. Then, in each hybrid and crop, were estimated the correlation coefficients for the 66 pairs of traits and determined the sample size necessary to estimate the correlation coefficients in four accuracy levels [amplitudes of the confidence interval of 95% (ACI(95%)) of 0.15, 0.25, 0.35 and 0.45], by resampling with replacement. The sample size varies among hybrids, crops and pairs of traits. Larger sample size is required to estimate the correlation coefficient between weakly correlated traits and smaller sample size is needed to estimate the correlation coefficient between highly correlated traits. Independently of hybrid, crop and pairs of traits, 375, 195 and 120 plants are sufficient, respectively, to estimate the correlation coefficients with maximum ACI(95%) of 0.25, 0.35 and 0.45.