Trend analysis Chesapeake Bay Glossary Glossary and Key Word List Definition: A formal statistical process used to determine the presence or absence of changes in measures of water quality over time or a geographic area. Trend Analysis EPA EV-Research-Research Resources-Analytical Methods &Protocols Taxonomy Definition: Formal statistical process used to determine the presence or absence of changes in measures of water quality over time or a geographic area. [Chesapeake Bay Glossary]