The Analysis of Different Approaches Related to the Measurement Uncertainty in Biomedical Calibration

Year 2007, Volume: 20 Issue: 3, 61 - 67, 29.03.2010

İrfan Karagöz , Serkan Cecelioğlu

Abstract

As a result of the calculation of expanded uncertainty, the measurement uncertainty defines an interval within which the measurand lies. Expanded uncertainty is generally calculated by using z-distribution in conjunction with coverage factor  k . But, by using z-distribution, correctly  finding the interval which the measurand lies within, with a specified confidence level, requires too many measurements which must be done repeatedly. In an ideal case, the number of measurements must approach infinity. Since this is not the case in practice, if the number of measurements is small, using Student’s factor t_ν,p  instead of coverage factor  k  results in the definition of a relatively wider interval and more accurate results. This situation is shown, as a result of an analysis done on a biomedical system, by calculating the measurement uncertainty and the interval within which the measurand lies in a confidence level of 95%, comparing two different approaches.

 

Key Words: Biomedical calibration, Measurement uncertainty, t-distribution, z-distribution

Keywords

Biomedical calibration, Measurement uncertainty, t-distribution, z-distribution

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• E1. For t-distribution, Student’s constant, tν p,ν , with normal distribution, where ν is the degree of freedom at the associated level of confidence, p. Degree of Freedom ν= N−1 t%95 t%99 1.729 1.725 1.721 1.717 1.714 1.711 1.708 1.706 1.703 1.701 1.699 1.697 1.684 1.68 1.66 1.658 1.98 ∞ 1.645 861 845 831 819 807 797 787 779 771 763 756 75 704 69 626 617 576 960 1.740 2.110 2.898 1.734 2.101 2.878