Sample size to estimate the mean and median of traits in flax

Abstract

The aim of this study was to determine the sample size (i.e., number of plants) required to estimate the mean and median of flax traits (Linum usitatissimum L.) of the cultivar CDC Normandy, with precision levels. In experimental area of 15 × 15 m (225 m2) at 134 days after sowing, 300 plants were collected randomly. In each plant, it was measured morphological (plant height and number of branches) and productive traits (number of capsules, fresh matter of capsules, fresh matter of aerial part without capsules, fresh matter of aerial part, dry matter of capsules, dry matter of aerial part without capsules, and dry matter of aerial part). For each trait, it was calculated measures of central tendency, variability, skewness, and kurtosis. It was determined the sample size by resampling with replacement of 10,000 resamples. In order to estimate the mean of morphological and pro­ductive traits of flax, cultivar CDC Normandy, with the amplitude of the confidence interval of 95% equal to 30% of the estimated mean, 81 plants are required. To estimate the median, with the same precision, it is necessary 161 plants.