Management: Briefs Selection of a Minimum Sample Size for Application of the Regression-Line–Percentile Technique

Proper application of the relative weight (Wr) index depends on development of a standard weight (Ws) equation for the target species. Development of Ws equations has been facilitated by the regression-line–percentile (RLP) technique, but the minimum data needed to develop a Ws equation with the RLP technique has not been investigated. We applied the bootstrap technique to data sets containing slope values from population log10 weight–log10 total length regressions for nine fish species (50–292 populations each). We randomly selected regression slopes at sequential intervals of five, and each iteration was repeated 100 times to determine the variance about the regression slope means. The sample variance for slopes was observed to decline in an exponential fashion. A minimum level of precision based on the sample variance (<0.002) provided a conservative estimate of necessary sample size (N ≥ 50). This variance benchmark is sufficient for the current level of precision required in the development and application of RLP-generated equations.