Predicting Effectiveness of Wood Preservatives From Small Sample Field Trials
Keywords:Box plots, censored data, nonparametric statistics
AbstractField tests of wood preservatives use groups of stakes treated at various retentions. Although only an average value is reported for a given group of stakes, the lifetime of individual stakes is quite variable. This paper explores presentations of data that reflect such variability. We also consider the feasibility of predicting the effectiveness of a preservative before all stakes fail. For sample sizes of ten replicate stakes, we suggest that reports include box plots of the actual failure times, and that studies use the sample median for the reported lifetime value rather than the sample mean and report the first quartile as a lower bound for the population average.
Colley, R. H. 1970. The practical meaning of preservative evaluation tests. Proceedings of the American Wood-Preservers' Association, pp. 16-37.nConover, W. J. 1980. Practical nonparametric statistics, 2nd ed. John Wiley and Sons, New York.nGillespie, T., H. P. Sedziak, and J. Krzyzewski. 1969. The analysis of service life experiments on wood treated with preservatives. Wood Sci. 2(2):73-76.nGjovik, L. R., and D. I. Gutzmer. 1989. Comparison of wood preservatives in stake tests. 1987 Progress report, USDA Forest Service, Forest Products Laboratory Research Note FPL-RN-02, Madison, WI.nHartford, W. H. 1972. The interpretation of test plot data. Proceedings of the American Wood-Preservers' Association, pp. 67-82.nKaplan, E. L., and P. Meier. 1958. Nonparametric estimation from incomplete observations. J. Statist. Assoc. 53:457-481.nLee, E. T. 1980. Statistical methods for survival data analysis. Wadsworth Press, Belmont, CA.nMacLean, J. D. 1957. Percentage removals and average life of railway ties. USDA Forest Service, Forest Products Laboratory, Report No. 886, Madison, WI.nNelson, W. 1982. Applied life data analysis. John Wiley and Sons, New York.nThorne, M. E. 1918. Relation between average life of ties and percentage of renewals. Proceedings of the American Wood-Preservers' Association, pp. 150-156.nVelleman, P. F., and D. C. Hoaglin. 1981. Applications, basics, and computing of exploratory data analysis. Duxbury Press, Belmont, CA.n
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