A guide for choosing which statistical test to use. From our Applied Environmental Statistics course:

Statistical tests can be classified into 5 types, based on the measurement scales of your response and explanatory variables. Are those scales continuous, or grouped?

Response variable
  • the variable you are trying to understand
  • usually plotted on the Y axis
  • continuous (1.4, 2.5, ...) or grouped (above vs. below detection limit)

Explanatory variables
  • variables used to explain Y
  • usually plotted on the X axis
  • continuous (1.4, 2.5, ...) or grouped (ag, urban, forest)

Choose (click on) your procedure based on whether your variables are continuous or grouped:

.Compare data among two or more groups
Continuous Y Grouped X
Compare differences among two or more groups

Continuous Y Continuous X
Relate a continuous Y variable to one or more continuous explanatory variables.

Continuous Y both Grouped and Continuous X
Is there 1 or more than 1 regression line?

Grouped Y Grouped X
Do percentages of Y categories (detect / nondetect) change between two or more groups (June vs. Sept)?

Grouped Y Continuous X
Do percentages (% hits) change as one or more explanatory variables (thickness) change?