A generalized estimating equation method for fitting autocorrelated ordinal score data with an application in horticultural research

TY - JOUR

T1 - A generalized estimating equation method for fitting autocorrelated ordinal score data with an application in horticultural research

AU - Parsons, N. R.

AU - Edmondson, R. N.

AU - Gilmour, S. G.

PY - 2006/8

Y1 - 2006/8

N2 - Generalized estimating equations for correlated repeated ordinal score data are developed assuming a proportional odds model and a working correlation structure based on a first-order autoregressive process. Repeated ordinal scores on the same experimental units, not necessarily with equally spaced time intervals, are assumed and a new algorithm for the joint estimation of the model regression parameters and the correlation coefficient is developed. Approximate standard errors for the estimated correlation coefficient are developed and a simulation study is used to compare the new methodology with existing methodology. The work was part of a project on post-harvest quality of pot-plants and the generalized estimating equation model is used to analyse data on poinsettia and begonia pot-plant quality deterioration over time. The relationship between the key attributes of plant quality and the quality and longevity of ornamental pot-plants during shelf and after-sales life is explored.

AB - Generalized estimating equations for correlated repeated ordinal score data are developed assuming a proportional odds model and a working correlation structure based on a first-order autoregressive process. Repeated ordinal scores on the same experimental units, not necessarily with equally spaced time intervals, are assumed and a new algorithm for the joint estimation of the model regression parameters and the correlation coefficient is developed. Approximate standard errors for the estimated correlation coefficient are developed and a simulation study is used to compare the new methodology with existing methodology. The work was part of a project on post-harvest quality of pot-plants and the generalized estimating equation model is used to analyse data on poinsettia and begonia pot-plant quality deterioration over time. The relationship between the key attributes of plant quality and the quality and longevity of ornamental pot-plants during shelf and after-sales life is explored.

KW - Generalized estimating equations

KW - Ordinal scores

KW - Plant quality scores

KW - Proportional odds model

KW - Repeated measures

UR - http://www.scopus.com/inward/record.url?scp=33746265584&partnerID=8YFLogxK

U2 - 10.1111/j.1467-9876.2006.00550.x

DO - 10.1111/j.1467-9876.2006.00550.x

M3 - Article

AN - SCOPUS:33746265584

SN - 0035-9254

VL - 55

SP - 507

EP - 524

JO - APPLIED STATISTICS

JF - APPLIED STATISTICS

IS - 4

ER -