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Corn Export Cargo Quality Report 2012/2013

Contents

  1. Export Cargo Quality Highlights
  2. Introduction
  3. Quality Test Results
  4. Moisture
  5. Chemical Composition
  6. Physical Factors
  7. Mycotoxins
  8. U.S. Corn Export System
  9. U.S. Export Corn Flow
  10. Impact of the Corn Market Channel on Quality
  11. U.S. Government Inspection and Grading
  12. Survey and Statistical Analysis Methods
  13. Survey Design and Sampling
  14. Statistical Analysis
  15. Testing Analysis Methods
  16. Corn Grading Factors
  17. Moisture
  18. Chemical Composition
  19. Physical Factors
  20. Mycotoxin Testing
  21. U.S. Corn Grades and Conversions
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V. SURVEY AND STATISTICAL ANALYSIS METHODS

A. Overview

The key points for the survey design and sampling, and statistical analysis for this Export Cargo Report 2012/13 are as follows:

  • Following the process developed for the Export Cargo Report 2011/12, samples were stratified according to Export Catchment Areas (ECAs) – the Gulf, Pacific Northwest, and Southern Rail.
  • To achieve a maximum ± 10% relative margin of error (Relative ME) for the U.S. Aggregate level and to ensure proportional sampling from each ECA, the targeted number of total samples was 426 samples to be collected from the ECAs as follows: 284 from the Gulf, 87 from the Pacific Northwest, and 55 from the Southern Rail.
  • Southern Rail ECA samples were provided by any of several official agencies designated by USDA’s Federal Grain Inspection Service (FGIS) that inspect and grade rail shipments of corn destined for export to Mexico. Gulf and Pacific Northwest samples were collected by FGIS field offices at ports in the respective ECAs.
  • Export inspections of shipments from the Southern Rail ECA (interior) did not generate the targeted number of samples for this report because there were very few interior shipments meeting the sampling criteria. As a result, only 7 samples were collected for the Southern Rail ECA. Nonetheless, the U.S. Aggregate averages for the quality factors were weighted according to the targeted proportion by ECA.
  • To evaluate the statistical validity of the number of samples surveyed, the relative margin of error (Relative ME) was calculated for each of the quality attributes at the U.S. Aggregate and the three ECA levels. The Relative ME for the quality factor results were less than ± 10% except for three attributes from the Pacific Northwest ECA – total damage, stress cracks, and stress crack index – and four attributes from the Southern Rail ECA – BCFM, total damage, stress cracks, and stress crack index.