Standard deviation may serve as a measure of uncertainty. In science, for example, the standard deviation of a group of repeated measurements helps scientists know how sure they are of the average number. When deciding whether measurements from an experiment agree with a prediction, the standard deviation of those measurements is very important. If the average number from the experiments is too far away from the predicted number (with the distance measured in standard deviations), then the theory being tested may not be right. For more information, see prediction interval.