University of North Carolina
University of North Carolina: Eric Notebook: Cross Sectional Studies [Pdf]
Explains what a cross-sectional study of a population is and how it compares with a cohort study. Its advantages, disadvantages, and limitations are discussed, and how it is used in studying health issues and risks. Includes two practice...
TeachEngineering
Teach Engineering: Dams
Through eight lessons, students are introduced to many facets of dams, including their basic components, the common types (all designed to resist strong forces), their primary benefits (electricity generation, water supply, flood...