The results are not a random sample of the vehicles on the road at all.

The results are for a random sample, and so any given child may show few or none of the problems.

Health officials say the reason such a study hasn't been done is the difficulty in getting a true random sample.

The study took a random sample of 1,600 households last July.

The control group was a random sample drawn from the general population.

For example, it may be impossible to use a random sample.

As an example, consider a random sample of size 6.

Thus the poll was not a random sample of Americans.

And that hour's data are not likely to represent a random sample of the public.

So it does not appear to be a random sample.