I am investigating the relationship between the surface area of leaves and the rate of transpiration?

Question

I just need some advice on which statistical test to use. I am pretty sure its the Spearman's rank correlation coefficient test but i just need a bit of confirmation.

I will be using a potometer to calculate the rate of water uptake at regular time intervals and I will note down the corresponding leaf surface area. And i will be comparing the results of two duifferent varieties of plants.

Answer 1

The Spearman's rank correlation is usually used only when there's a bivariate population (one population showing two differing sets of values for the same characteristic).  You would seem to be comparing the correlation coefficient of two different populations (each species).  It would seem to me (and it's been a while since my stats classes) that a Fisher z transformation would be a better choice.

You could also try posting this question in the mathmatics section, since yours is more of a statistics question than a botany question, and see what answers you get there.