Evaluation of Measurement Data

Abstract

In a metrology laboratory, measurements are carried out assuming that measuring instruments are unbiased; hence all measured values derived from the observations of the measuring instrument belong to a normal distribution. In order to calculate the value of a measurand (output variable), we take observations from the measuring instruments, and apply known corrections from the calibration certificate and any corrections due to environmental parameters such as temperature, pressure and humidity of surrounding air or corrections due to the time elapsed since the calibration of measuring instrument or standard used. To assess the quality of the measured values Dixon test is applied (Sect.4.2). If there is more than one sample, individual mean of each sample is evaluated for quality (Sect.4.3). Quality of variances obtained for different samples is assessed (Sect.4.4 onward). After doing all this drill, one should find out all sources of uncertainty, calculate the contribution from each source in form of variance along with degrees of freedom and combine the variances from all sources. State the results together with uncertainty of measurement.