Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-011106-155345


Document Typethesis
Author NameHuang, Fang
URNetd-011106-155345
TitleModeling Patterns of Small Scale Spatial Variation in Soil
DegreeMS
DepartmentMathematical Sciences
Advisors
  • Dr. Jayson D. Wilbur, Advisor
  • Keywords
  • spatial variations
  • nested random effects models
  • semivariogram models
  • kriging methods
  • multiple logistic regression models
  • missing
  • multiple imputation
  • Date of Presentation/Defense2005-12-09
    Availability unrestricted

    Abstract

    The microbial communities found in soils are inherently heterogeneous and often exhibit spatial variations on a small scale. Becker et al. (2006) investigate this phenomenon and present statistical analyses to support their findings. In this project, alternative statistical methods and models are considered and employed in a re-analysis of the data from Becker. First, parametric nested random effects models are considered as an alternative to the nonparametric semivariogram models and kriging methods employed by Becker to analyze patterns of spatial variation. Second, multiple logistic regression models are employed to investigate factors influencing microbial community structure as an alternative to the simple logistic models used by Becker. Additionally, the microbial community profile data of Becker were unobservable at several points in the spatial grid. The Becker analysis assumes that the data are missing completely at random and as such have relatively little impact on inference. In this re-analysis, this assumption is investigated and it is shown that the pattern of missingness is correlated with both metabolic potential and spatial coordinates and thus provides useful information that was previously ignored by Becker. Multiple imputation methods are employed to incorporate the information present in the missing data pattern and results are compared with those of Becker.

    Files
  • huang.pdf

  • Browse by Author | Browse by Department | Search all available ETDs

    [WPI] [Library] [Home] [Top]

    Questions? Email etd-questions@wpi.edu
    Maintained by webmaster@wpi.edu