Intuitions about Power

What is it about?

When doing research a researcher wants that his or her study has a high probability of showing a statistical significant effect when the effect he or she is interested in is real. This probability is called the power and researchers can increase this probability easiest by using a larger sample size. Unfortunately, only a small proportion of researchers uses power analyses to make sample size decisions and their intuitions about power and sample size are flawed. Especially with small to moderate effects, researchers overestimate the power of these designs and underestimate the sample sizes needed for .80 power. This has resulted in many underpowered studies in Psychology.

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Why is it important?

Studies should be well powered to prevent research waste (many small studies with inconclusive results). Our studies shows that intuitions of researchers about statistical power are often wrong. Thus researchers should do formal power analyses before starting their research.