United States
OeP8rtment
of
Agriculture
,
Statistical
Reporting
Service
Statistical
Research
Division
SRS Staff Report
Number YRB-09
November 1985
Covariance
Analysis of Soybean
Objective Yield
Maturity Categories
7, 8 & 9
Robert Battaglia
ABSTRACT
KEYWORDS
COVARIANCE ANALYSIS OF
SOYBEAN OBJECTIVE YIELD
MATURITY CATEGORIES 7, 8 &: 9 By Robert J. Battaglia,
Statistical
Research Division, Statistical
Reporting Service, U.S. Department
of
Agriculture, Washington, D.C. 20250. November 1985. Staff Report No.
YRB-85-09.
Covariance
analysis
techniques were used to examine
the effects
of
maturity category and year on forecast models in the soybean objective
yield program. Models were constructed
using October data from 1977
to 1983. Results showed that forecast models from maturity categories
7, 8 &: 9 could not be operationally
combined into one October forecast
model without some loss in model
fit.
The year effect,
which was
significant
in some states,
shows that an unusual year can affect
the
slope and intercept of a forecast model.
Covariance
analysis, ma turi ty categories,
forecast models, Soybean
Objective Yield.
********************************************************
*
*
ACKNOWLEDGMENT
* This paper was prepared
for
limited
distribution
to
the
research
*
* community outside
the U.S. Department
of Agriculture.
The views *
* expressed herein are not necessarily
those of SRS or USDA.
*
*
********************************************************
The author
thanks Ron Steele for his assistance with the analysis, and
for the helpful comments from Tom Birkett, Ned Jones and Ron Fecso.
Washington, D.C.
-1-
November 1985
,
CONTENTS
SUMMARY
INTRODUCTION
METHODS
RESULTS
RECOMMENDA TIONS
REFERENCES
APPENDIX
l. ••Maturity
Category
Definitions
APPENDIX
2•••Fixed-Variable
Forecast
Models
APPENDIX
3•••Covariance
Models
APPENDIX
4•••Forecasting
from Covariance
Models
-ll-
PAGE
iii
1
2
3
8
9
10
11
13
14
SUMMARY
The purpose of this research was to determine if soybean pods per plant
forecast models for maturity
categories 7, 8 &: 9