Optimum Sample Size to Detect Perturbation Effects: The ...

Power analysis for sample size estimations 7
Fig. 3. Power curves for ANOVA design for rocky shores east habitat with a. 10 % (n = 130) and b. 25 %
(n = 21) of variability (dispersion coefficient). Dotted line represents the minimum acceptable power of 0.80.
Thus, an incorrect sampling program to assess a potential impact could have negative
consequences on the marine natural systems, especially when the null hypothesis (e.g.,
non-perturbation) was not rejected and simultaneously a posteriori statistical power
was not determined, which finally determines the quality of our conclusions. However,
in those cases when the null hypothesis was not rejected with low power, it is strongly
recommended to use the precautionary principle as an important decision-making tool
for improving management polices.