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:
.
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?