An overpowered study has too large a sample size and wastes resources. We will show how the power and required sample size can be calculated for several common types of studies, mention software that can be used for the necessary calculations, and discuss additional considerations.

When a study is underpowered?

An underpowered study is one in which insufficient individuals were enrolled (or data points obtained) to draw a meaningful conclusion. These are potentially bad. They expose study participants to risk without providing meaningful knowledge.

Can a study have too much power?

Power is usually set at 80%. This means that if there are true effects to be found in 100 different studies with 80% power, only 80 out of 100 statistical tests will actually detect them. ... On the flip side, too much power means your tests are highly sensitive to true effects, including very small ones.