is the distribution of pine trees related to soil type?
You have noticed that pine trees grow well in some parts of the woods, but not others. You speculate that the distribution of pines is related to drainage, that is, that pines prefer a very well-drained soil, while they do poorly in wet areas. You sample soil from evenly spaced plots throughout the forest, two days after a heavy rain. You find that you can describe each plot as belonging to one of three categories of soil: dry (sample falls apart in your hand), loamy (holds shape if you squeeze it, falls apart if you drop it), and wet (muddy – you can squeeze lots of water out, soil tends to run through your fingers). Now, if soil drainage has no bearing on the distribution of pines, then you would expect half of the plots of each soil type to have pine trees, provided you sampled enough plots. That is, the expected frequency of soil types in plots with pine trees is 50% dry, 30% loamy, and 20% wet. An expected frequency assumes that catagories have no effect on the variable being meas
