Basics of estimating measurement uncertainty.

* All measurements are imperfect and have many potential sources of variation. * An estimate of measurement uncertainty (MU) provides an interval of values within which the true value is believed to lie with a stated probability, and is therefore a quantitative indication of the reliability of a measurement. * MU estimates are essential for assessing whether methods are suitable for clinical use and for comparison of results of a similar type. * MU estimates can help identify method limitations and opportunities for improvement.