Title page for ETD etd-10282010-173615


Type of Document Master's Thesis
Author Schlub, Karl Anthony
URN etd-10282010-173615
Title Investigating the Ironwood Tree (Casuarina Equisetifolia) Decline on Guam Using Applied Multinomial Modeling
Degree Master of Applied Statistics (M.Ap.Stat.)
Department Experimental Statistics
Advisory Committee
Advisor Name Title
Marx, Brian D. Committee Chair
Li, Bin Committee Member
Wang, Jing Committee Member
Keywords
  • logit
  • categorical
  • ordinal response
  • regression
  • statistics
Date of Defense 2010-10-13
Availability unrestricted
Abstract
The ironwood tree (Casuarina equisetifolia), a protector of coastlines of the sub-tropical and tropical Western Pacific, is in decline on the island of Guam where aggressive data collection and efforts to mitigate the problem are underway. For each sampled tree the level of decline was measured on an ordinal scale consisting of five categories ranging from healthy to near dead. Several predictors were also measured including tree diameter, fire damage, typhoon damage, presence or absence of termites, presence or absence of basidiocarps, and various geographical or cultural factors. The five decline response levels can be viewed as categories of a multinomial distribution where the multinomial probability profile depends on the levels of these various predictors. Such data structure is well suited to a proportional odds model thereby leading to odds ratios involving cumulative probabilities which can be estimated and summarized using information from the predictor coefficient. Various modeling techniques were applied to address data set issues: reduced logistic models, spatial relationships of residuals using latitude and longitude coordinates, and correlation structure induced by the fact that trees were sampled in clusters at various sites. Among our findings, factors related to ironwood decline were found to be basidiocarps, termites, and level of human management.
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