The ability to detect experimental effects is undermined in studies that lack power.
Statistical testing provides a paradigm for deciding whether the data are or are not typical of the values expected when the hypothesis is true. Because our objective is usually to detect a departure from the null hypothesis, it is useful to define an alternative hypothesis that expresses the distribution of observations when the null is false. The difference between the distributions captures the experimental effect, and the probability of detecting the effect is the statistical power.
Via Niklaus Grunwald