Why low power is undesirable

This chapter addresses the questions why a low-powered study has a high probability of failing to detect genuine effects. It highlights how low power makes drawing useful inferences from failure to reject the null hypothesis more difficult. It shows that the risk that a significant result is a Type I error increases if an experiment is low-powered and analyses why low power inflates the effect sizes associated with statistical significance. The chapter clarifies that the statistical power of an experiment is one minus the probability of making a Type II error based on the outcome of that experiment. It confirms that low power is undesirable because it means an increased risk of a Type II error, emphasizing that the lower the power, the less likely it is that a significant result is actually triggered by a real underlying effect.