To test whether a radio signal contains a message or constitutes random noise, an interval of time is sub-divided into a number of very short intervals, and for each of these it is determined whether the signal strength exceeds, E, or does not exceed, N, a certain level of background noise. Test at the 0.01 level of significance whether the following arrangement, thus obtained, may be regarded as random and hence that the signal does not contain a message:
N N N E N E N E N E E E N E E E N E E N E N E E N E E N N E N E E E N E N N N E N N E N N N N E