Improvements in automated reliability growth plotting and estimation

Calculations of Instantaneous MTBF have gotten sloppy since J. T. Duane [1] and E. O. Codier [2] published their papers on the subject 43 years ago. Codier presented the following notes on plotting the line through the points in his definitive description of Duane´s Reliability Growth calculation methods that he presented at the 1968 Annual Symposium on Reliability: ldr The latter points, having more information content, must be given more weight than earlier points and ldr The normal curve fitting procedure of drawing the line through the ldquocenter of gravityrdquo of all the points should not be used. ldr Unless the data is exceptionally noisy, the best procedure is to start the line on the last data point and seek the region of highest density of points to the left of it. These principals for estimating MTBF from non-homogeneous data are not being followed and the result is a less than accurate estimation of current (aka, instantaneous) MTBF.