INFLUENCE OF SAMPLE-SIZE ON PRECISION OF HERITABILITY AND EXPECTED SELECTION RESPONSE IN RED-CLOVER

Limited attention has been given to the effect of sample size on the p recision of heritability estimates and expected selection responses. T he objectives of this study were to evaluate the effect of sample size on the point estimate, its sampling error and interval width. Monte C arlo simulation and non-parametric bootstrap were used to estimate par ameters in a red clover (Trifolium pratense L.) data set. We conducted separate analyses for two and four replications, and for combinations of six, 12, 24, 42 and 66 families, each having three, six, nine, 12 and 18 plants. Results showed that the effect of increasing number of families and replications on reduction of sampling error and interval width was greater than that of increasing plants per family. The sampl ing error and interval width of parameters decreased at a decreasing r ate as sample size increased. To reduce the chances of having negative estimates of family variance components and to achieve a narrow confi dence interval, an experiment of 42 families, each having six seedling s in four replications would be required.