Correlation

[Fernando Andreacci]

Hello,
My name is Fernando, I'm a biologist and I also have many statistics questions. Hope you can help me.

First of all:

I'm working with tree radial growth and I have measuraments over 10 months (from september 2010 to june 2011).

This is an average from 10 trees:

0.98, 1.575, 1.69, 2.16, 2.7775, 3.0275, 3.46, 3.7275, 3.7825, 3.7525 

I also have metereological data from september to june (ie. precipitation (mm)).

128.92, 129.19, 114.22, 148.91, 190.63, 145.26, 124.11, 77.65, 98.69, 94.27 

If I make a chart with this data, I can visualize a positive correlation during the first 6 months (growing season), but the last 4 I get a negative correlation. However, this negative correlation is due to the biology of the trees, see:

From march to june there are less precipitation and temperature is also low, so trees do not grow (grow just a lit bit). It is and expecpected behavior.

How can I express this through statistics and prove its significance?

Thanks

[mintsmike]

Firstly, make a scatter plot with your data (not the average tree length, but all of the measurements) against precipitation (mm). Try a linear regression. If that's suitable, then you could test for significance of the slope estimate, b. You could test for significance of the Pearson product-moment correlation coefficient, or the coefficient of determination. Just say if you don't know these test statistics