Tham khảo tài liệu 'measurement process characterization_11', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | . Analysis of variability Level-1 LK repeatability standard deviations can be computed from the data The measurements from the nested design are denoted by Equations corresponding to the tabular analysis are shown below. Level-1 repeatability standard deviations s 1lk are pooled over the K days and L runs. Individual standard deviations with J -1 degrees of freedom each are computed from J repetitions as Silk where Ylk. - - 2 h y Level-2 L reproducibility standard deviations can be computed from the data The level-2 standard deviation s2l is pooled over the L runs. Individual standard deviations with K -1 degrees of freedom each are computed from K daily averages as where Yi - ị ỈỸỉk. K jt l http div898 handbook mpc section4 4 of 5 5 1 2006 10 12 39 AM . Analysis of variability Level-3 A single global standard deviation can be computed from the L-run averages A level-3 standard deviation with L -1 degrees of freedom is computed from the L-run averages as where Relationship to uncertainty for a test item The standard deviation that defines the uncertainty for a single measurement on a test item is given by where the pooled values s1 and s2 are the usual and There may be other sources of uncertainty in the measurement process that must be accounted for in a formal analysis of uncertainty. NIST SEMATECH HOME TOOLS AIDS SEAftCH BACK NEXT http div898 handbook mpc section4 5 of 5 5 1 2006 10 12 39 AM . Analysis of repeatability TOOLS 4 AIDS SEARCH BACK next 2. Measurement Process Characterization . Gauge R R studies . Analysis of variability . Analysis of repeatability Case study The repeatability quantifies the basic precision for the gauge. A level-1 repeatability Resistivity standard deviation is computed for each group of J repetitions and a graphical analysis is probes recommended for deciding if repeatability is dependent on the check standard the operator or the gauge. Two graphs
