Peittävyystekijä

Peittävyystekijä, often translated as coverage factor or simply factor k, is a multiplier used in calculating expanded uncertainty in metrology and statistics. It is a dimensionless quantity that defines the level of confidence associated with a given interval. When calculating the expanded uncertainty, the standard uncertainty (also known as the combined standard uncertainty) is multiplied by the coverage factor to obtain the interval within which the true value of a measured quantity is expected to lie with a specified level of confidence.

The value of the coverage factor is typically determined based on the desired confidence level and the degrees of freedom associated with the uncertainty. For a large number of independent measurements or when the uncertainty is estimated using a normal distribution with a high degree of confidence, a common coverage factor is k=2, which corresponds to approximately a 95% confidence level. In some cases, particularly when degrees of freedom are low, the Student's t-distribution is used to determine a coverage factor that ensures the desired confidence level. The selection and application of the coverage factor are crucial for providing a meaningful and reliable estimate of the uncertainty of a measurement. It ensures that the reported uncertainty interval accurately reflects the likelihood of containing the true value.