Date of Award

2002

Degree Type

Thesis

Degree Name

Master of Science in Statistics

Department

Computer Science and Statistics

First Advisor

James S. Heltshe

Abstract

This study simulates individuals that are modeled after benthic macroinvertebrate populations from streams in Vermont. Using the EPA biological scoring criteria for assessing the overall condition of streams, we analyzed two metrics (parameters) associated with these criteria. The two metrics, taxa richness and Community Loss Index (CLI) have "critical" values that were set by the EPA. These "critical" values although well established are not be justified statistically. In order to analyze these "critical" values, we analyzed three different options: sample size, taxonomic level, and changing the "critical" value to achieve our goal.

We asked the question, how often would two samples of 100 organisms, which are both taken from the same reference population, be considered different? By simulating two different samples from the same population 100 times, we could obtain an estimate of percentage of times one would conclude the population to be different. Generally, the best results occurred at the genus level with a slight modification to the "critical" value and a sample size of 100 for the taxa richness metric. For CLI, the genus level with a sample size of 200 and no "critical" value change produced the best results.

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