Experimental design in the presence of covariates

Avcıoğlu, M Didem
Experimental design methods have broad coverage of application areas. Usually, basic goal in experimental design methods is to compare the effect of controllable experimental factors on the response and locate the interest on the one, which is most effective. However, in many experimental situations, responses are not only affected by the controllable experimental factors, but also by uncontrollable variates, usually named as covariates. Main aim in these models is to relate the response to both the controllable and uncontrollable variates and investigate the effects of the variates on the response. Analysis of covariance (ANCOVA) is a frequently used method of analysis, especially in the biological sciences. Nevertheless, most of the work done on this model is based on the normality assumption of the error distribution. In practice, however, non-normal distributions occur more frequently. The aim of this study is to investigate this model under non-normality and to develop robust and efficient methods for estimation and hypothesis testing.


Evaluation of the NDVI in plant community composition mapping: a case study of Tersakan Valley, Amasya County, Turkey
DOĞAN, Hakan Mete; Celep, Ferhat; Karaer, Fergan (Informa UK Limited, 2009-01-01)
Mapping the composition of plant community types requires reliable spatial data obtained from field surveys and satellite-derived indices. The normalized difference vegetation index (NDVI) is the simplest and most frequently used index in plant applications. If relationships between the NDVI and plant cover abundance are determined, this information can be used in the mapping process. In this study, we investigated these possible connections for mapping the plant community composition of Tersakan Valley in ...
Effects of Content Balancing and Item Selection Method on Ability Estimation in Computerized Adaptive Tests
Sahin, Alper; ÖZBAŞI, DURMUŞ (2017-01-01)
Purpose: This study aims to reveal effects of content balancing and item selection method on ability estimation in computerized adaptive tests by comparing Fisher's maximum information (FMI) and likelihood weighted information (LWI) methods. Research Methods: Four groups of examinees (250, 500, 750, 1000) and a bank of 500 items with 10 different content domains were generated through Monte Carlo simulations. Examinee ability was estimated by fixing all settings except for the item selection methods mention...
Conceptual data modeling of multimedia database applications
Aygun, S; Yazıcı, Adnan; Arica, N (1998-08-07)
In this paper, we present a conceptual data model for multimedia database applications based on ExIFO(2) model. The ExIFO(2) data model is chosen as the conceptual model since it handles both complex objects along with their uncertain and imprecise properties. We enhanced this conceptual model in order to meet the multimedia data requirements. In addition to uncertain and imprecise information, we present a way of handling relationships among objects of multimedia database applications. Events that might be...
Gokdogan, Gokhan; Vural, Elif (2017-09-28)
An important research topic of the recent years has been to understand and analyze manifold-modeled data for clustering and classification applications. Most clustering methods developed for data of non-linear and low-dimensional structure are based on local linearity assumptions. However, clustering algorithms based on locally linear representations can tolerate difficult sampling conditions only to some extent, and may fail for scarcely sampled data manifolds or at high-curvature regions. In this paper, w...
Applications of estimation techniques on genetic and other types of data
Aslan, Murat; Akkaya, Ayşen; Department of Statistics (2003)
The parameters of genetic and other types of data, particularly with small samples, are estimated by using method of moments, least squares, minimum chi- square, maximum likelihood and modified maximum likelihood estimation methods. These methods are also compared in terms of their efficiencies and robustness property.
Citation Formats
M. D. Avcıoğlu, “Experimental design in the presence of covariates,” M.S. - Master of Science, Middle East Technical University, 2003.