Trend Analysis to Improve Efficiency of Agronomic Trials in Flue-Cured Tobacco
The desire to improve statistical evaluation efficiency in flue-cured tobacco (Nicotiana tabacum L.) cultivar trials and the inconvenience of restricted entry numbers in incomplete block designs prompted an investigation into a statistical procedure known as the trend analysis. The objective was to determine relative efficiency of the trend procedure compared to the randomized, complete block design by examining error variances from both analyses of variance. Eleven traits on all entries of the North Carolina Official Flue-Cured Tobacco Variety Trials were examined at five environments. Relative efficiency of trend compared to the randomized, complete block design ranged from 97 to 161% for traits and environments. Only one trait, number of ground suckers, showed no improvement in precision (101%) from trend analysis while quality indicators ($/kg and grade index) showed the greatest improvement (126 and 124%) when averaged for all environments. The data revealed that blocking may be effective for one trait and not another.
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