It simply cannot be assumed that samples selected for their distinctiveness on one variable will vary randomly on others.

But after that, his cycles began varying randomly, ranging from 18 to 52 hours.

Bottom sediments varied almost randomly, with patches of sand, or gravel, or mud in different places.

This means that the result of each salvo also varies randomly.

By this we mean that machine tool errors obey cause-and-effect relationships, and do not vary randomly for no reason.

Measurements show trends with time rather than varying randomly about a mean.

The way the receiver is set varies randomly from photon to photon.

Because the position of the photographs varied randomly from trial to trial, sequences could not be learned by motor imitation.

The amplitude and phase of the surface wave at any given point are fixed, but both vary randomly across the surface.

They add together to give a resultant wave whose amplitude, and therefore intensity varies randomly.