Abstract
Generally, the sample size in a sample survey can be calculated according to the coefficient of variation among the characters to be studied and also the desired precision of the survey. In the case of rice plants, however, sufficient information is not available regarding coefficient of variation in their quantitative characters. In order to obtain sample size of a sample survey in a field experiment, the coefficients of variations of characters were investigated under various conditions for a period of three years. This study was made using hand-transplanted rice of the fixed number of seedlings per hill as generally practiced in cultivation experiments. The difference of the variation coefficients due to the year, field, cropping season, variety of the crop, and the direction of planting rows was small unless cultivation management was exceptionally loose, and it was judged that differences in these cultivation conditions hardly affect the sample size for a crop survey. The difference of the variation coefficients due to differring planting densities was too large to ignore. In this study, using rice plants grown in a standard density, statistical estimation was made on the coefficients of variation in quantitative characters at each growth period of the max tiller number stage, full heading stage and maturing stage. Then, the sample sizes in six cases of differing desired precision were computed, using the estimated coefficient of variation.
