Which of the following is the best interpretation of the power of a significance test?

A) Power is the probability of detecting an effect if no effect exists.
B) Power is the probability of detecting an effect if an effect exists.
C) Power is the probability of detecting an effect whether or not an effect exists.
D) Power is the probability of not detecting an effect if no effect exists.
E) Power is the probability of not detecting an effect if an effect exists.