Weighted Versus Unweighted Estimates Using Scheffé's Mixture Model for Symmetrical Error Variances Patterns.
作者:
JohnA. Cornell,
期刊:
Technometrics
(Taylor Available online 1977)
卷期:
Volume 19,
issue 3
页码: 237-247
ISSN:0040-1706
年代: 1977
DOI:10.1080/00401706.1977.10489545
出版商: Taylor & Francis Group
关键词: Mixture components;Component axes;Error variance;Weighted least squares estimates
数据来源: Taylor
摘要:
When fitting the first-degree Scheffé polynomial and the assumption of homogeneous error variance is suspect, one suggestion made in this paper is to place the design points in a symmetrical arrangement and along the component axes. For if the magnitude of the error variance (or observation variance) follows one of several conceivable symmetrical patterns, the use of the symmetrical axial designs will result in the existence of certain relationships between the parameter estimates obtained using an unweighted analysis versus using a weighted analysis. Some results which carry over to the parameter estimates in a second-degree polynomial forq= 3, 4 and 5 are presented along with two real examples.
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