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

Yıl 2007, Cilt: 20 Sayı: 3, 61 - 67, 29.03.2010

İrfan Karagöz , Serkan Cecelioğlu

Öz

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

Anahtar Kelimeler

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

Kaynakça

• Eroğul, O., Karagöz, İ., Üreten, O., “Biyomedikal Mühendislik Birimlerinin Hastanelerdeki Kalite Güvence Sistemine Katkıları ve Etkinliği”, Yöneylem Araştırması ve Endüstri Mühendisliği XX. Ulusal Kongresi, 227, Kara Harp Okulu, Ankara, 1999.
• Karagöz, İ., ” Hastane Organizasyonu İçinde Biyomedikal ve Klinik Mühendislik Birimlerinin İşlev ve Önemi ”, Sağlık Hizmetlerinde Toplam Kalite Yönetimi ve Performans Ölçümü Sempozyumu, 13-26, Ankara,1996.
• “Evolving Needs for Metrology in Trade, Industry and Society and the Role of the BIPM”, CIPM, TS EN ISO 9001, Türk Standardları Enstitüsü, TSE, 1994.
• Karagöz, İ., Tıbbi Teknoloji Yönetimi, Haberal Eğitim Vakfı, Ankara, 1998. Karagöz,
• İ., “Hastanelerde Kullanılan Tıp Teknolojilerine Klinik Mühendisliğinin Etkileri”, Tıp ve Hastane Alanındaki Fransız Teknolojileri Semineri, 49-54, İstanbul, 1998.
• Taylor, B.N., Kuyatt, C.E.,”Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results”, NIST Technical Note 1297, 1994 Edition, 1993.
• Sadıkhov, E., Kangı, R., Uğur, S., “Ölçüm Belirsizliği”, Ulusal Metroloji Enstitüsü, UME 016, 1995.
• “The Expression of Uncertainty and Confidence in Measurement”, UKAS, Edition 2, 2006. APPENDIX
• 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