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On the Statistical Analysis of Ordinal Data When Extravariation is Present
Author(s) -
Jansen J.
Publication year - 1990
Publication title -
journal of the royal statistical society: series c (applied statistics)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.205
H-Index - 72
eISSN - 1467-9876
pISSN - 0035-9254
DOI - 10.2307/2347813
Subject(s) - ordinal data , statistics , statistical analysis , ordinal optimization , mathematics , computer science , econometrics
SUMMARY Threshold models can be useful for analysing ordered categorical data, like ratings. Such models provide a link between the ordinal scale of measurement and a linear scale on which treatments are supposed to act. In this paper a simple agricultural plot experiment is considered with two sources of variation, namely between‐plot variation and within‐plot variation. So far, methods for analysing ordered categorical data are not capable of handling such a situation adequately. It is shown that for a threshold model with two sources of variation maximum likelihood estimates can be obtained by iterative weighted least squares. The computer package Genstat is used to carry out the computations. to illustrate the methods an example concerning damage in strawberries due to the fungus Phytophtora fragariae is given.