I want to determine if there is a significant difference in mean water content between two patches of soil. Which test should I use?

Question

I come across two problems. First, I monitored both patches at 10cm and 30cm over a two month period. Since the two patches are impacted by precipitation over time, I'm assuming that the samples are not independent. Second, my sample size is fairly small with n=6 for both patches of soil at both depths (10cm and 30cm). Therefore I'm wondering which statistics test I can use to compare the means?

Answer 1

If you simply want to compare the 10 cm patch to the 30 cm patch at a single time point, or compare the 10 cm patch to another 10 cm patch at 2 time points, a simple student's t-test is acceptable.  If you want to make all of the various comparisons of 10cm and 30cm patches across all the time points, you would need a two way ANOVA, with a post hoc test (there are many to choose from).