One form of cross-validation leaves out a single observation at a time; this is similar to the jackknife.

Asked what might be concluded from the single observation, the biologist says, "All sheep are black."

The combination of different observations taken under the same conditions contrary to simply trying one's best to observe and record a single observation accurately.

By it the right ascension and the declination of a star may be measured in a single observation.

He'd assumed something about them, an assumption based on a single observation.

'Yet this single observation is no true test,' he stated.

Indeed, estimates the expected log-likelihood of a single observation in the model.

But if you would make one single observation for me on Cypripedium, I should be glad.

A single observation is written on each piece of paper.

A single seemingly innocuous observation by either of us can plunge him into depression or even anger.