Ecology 5th Edition by Manuel Molles

Exercise 4

Suppose that during a field study you find a positive correlation between some variable X and another variable Y-for example, between higher concentrations of the stable isotope C 13 in the tissues of migrating redstarts and later arrival dates on their northern breeding grounds (see chapter 1, p. 4). Does this positive correlation demonstrate that an increase in X directly causes an increase in Y?