ENV330H5 Lecture Notes - Lecture 2: Herbicide, Lichen, Eutrophication
Document Summary
Can address a research question by exploiting the natural variation (spatial; temporal) in the data to suggest causal relationships. Observational studies: real world effects examining existing factors. Simple to design and conduct reduces the number of potential errors in design. Susceptible to confounding factors and reverse causation. E. g. : abundance/growth of conifers over a moisture gradient . Can be conducted over large temporal & spatial scales. No variables are controlled may be many confounding (nuisance) variables. Variation in hypothesized causal factor may not be sufficient to draw inferences. System is manipulated: all or part is subjected to specific treatments(including a control. Designed to address a research question by controlling variation in other factors to identify and describe causal relationships randomized, controlled experiments are an effective way to test predictions about causal relationships. Other variables are controlled treatments are replicated results. Can be more complicated/expensive to design, set up. Changing one factor may have unintended effects on others, confounding.
