Intro
What question did you ask in your project?
Is bark depth (of honey locust trees) a factor influenced by air pollution?
What data did you collect?
Collected the bark depth and trunk diameter of 15 urban and 15 rural trees (30 total)
What did you find?
Urban bark depth averaged 1.45cm, and rural: 0.96cm
What do the results show?
Urban bark depth is consistently thicker than rural bark depth
Why did you ask your question?
To expand the idea of air pollution's impact on plants/trees
How did you collect your data?
Used a bark gauge and tree tape measurer
Is there a relationship between bark depth and trunk diameter?
Yes – they are positively correlated
What do the results mean?
Pollution DOES have an impact on bark depth
What was your hypothesis?
Air pollution selects for thicker bark – urban trees would have thicker bark than rural trees
What tests did you use?
T-test between urban and rural & linear regression between bark depth and trunk diameter
How did you analyze bark depth without trunk diameter's influence?
Analyzed the residuals from the linear regression test
Why does this matter?
Proves how air pollution selects for thicker trees – natural selection by environmental factors