Confidence level

A measure usually associated with the comparison of observed value(s) with a probability density function (pdf). It expresses the probability that the observation is as far as observed or further away from the most probable value of the pdf, i.e., it corresponds to the integral over the pdf from the observed value to infinity. Differences in interpretation exist, e.g. deviations on both sides may be considered, or the integral may extend over integration limits defined from case to case (like over all ``large deviations).

A confidence interval, bounded by confidence limits, is an estimate for the range of values which an unkown parameter could take, given a confidence level. Confidence levels are often expressed as a percentage, e.g. it is 95% likely that a value of 11.07 or larger does not belong to a distribution with five degrees of freedom.