Power

notion

We reject the notion that we are alone in the universe and sweep the skies with powerful radio telescopes, looking for the faintest signal from intelligent life. Since nothing has been heard or received, except the primordial cosmic hiss, is the silence strong evidence that we are indeed alone? The answer, you will say, depends on the probability that if there were intelligent extraterrestrial life our sweeps of the sky would have detected it. This probability is called the power of our procedure. In statistics, a test procedure is said to have high power if it is very likely to detect an effect when one exists; conversely, it has low power if an effect could easily escape detection. Thus, if our test has high power, we are justified in treating the negative outcome as affirmative evidence that there is no extraterrestrial life, but if our test lacks such power, the negative outcome is merely inconclusive.