C. Statistical Analysis
The sample test results for the grade factors, moisture, chemical composition, and physical factors were summarized as the U.S. Export Aggregate and also by the two Export Outlets – NOLA and Texas. Contract grades are described in the “Sorghum Export System” section on page 39. For this 2015/2016 Export Cargo Survey, all of the export samples received were from sublots with contracts that were specified as grade U.S. No. 2 or better, which is the most common grade for which U.S. sorghum export contracts are written.
The Council followed standard statistical techniques employed for proportionate stratified sampling, including weighted averages and standard deviations, for analyzing the export results. Export inspections of shipments generated 136 samples from the Texas EO and 46 samples from the NOLA EO. Since the number of samples collected in each EO was in excess of the targeted number of samples, the U.S. Export Aggregate averages for the quality factors were weighted using the original sampling proportions.
The Relative ME was calculated for each of the quality factors tested for this study at the U.S. Export Aggregate level, and the Relative ME was less than ± 10% for all the quality attributes measured.
References in the summary tables in the “Export Quality Test Results” section to statistical differences were validated by 2-tailed t-tests at the 95% confidence level. The t-tests were calculated between factors in the 2015/2016 Harvest Survey and the 2015/2016 Export Cargo Survey.