A graphical guide for choosing which statistical test best fits your objectives. From our Applied Environmental Statistics course.

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Some definitions:

Statistical tests can be classified into 5 types, based on the measurement scales of your response and explanatory variables.

Are those scales

◦ the variable you are trying to understand

◦ usually plotted on the Y axis

◦ can be continuous (1.4, 2.5, ...) or grouped (above detection limit, below detection limit)

◦ variable used to explain Y

◦ usually plotted on the X axis

◦ can be continuous (1.4, 2.5, ...) or grouped (ag, urban, forest)

Think about how you might plot the results of your data analysis. Choose (click on) a procedure based on whether your response and explanatory 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?