Fig. 2.

Probability (power) of detecting a statistically significant (α = 0.05) treatment effect in total C concentration from the Long-Term Ecological Research experiment (randomized complete block design [RCBD] with 30 samples: six replicate plots and five subsamples per plot) as a function of relative differences between no-till (NT) and conventional tillage (CT) treatments for surface, middle, and deep soil layers (based on data from Syswerda et al. 2011). The numbers above each bar represent the number of subsamples that need to be taken in each of six replicated plots of this RCBD experiment to detect the hypothesized differences between CT and NT treatments with 90% probability (power) at α = 0.05.