Archived posting to the Leica Users Group, 1997/06/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Otto wrote: >>I did call the figure "MRBF, average" and I hope it passes critical eyes. The 4 bodies were turned around in use, trying to accomplish an even load. However no exact figures on how many rolls which body actually did were recorded. Nor did I record any max or min rolls before a failure occurred.<< You are correct to quote the MRBF of 322.6 rolls for your 4 bodies. What I meant was if you take ANY RTS III randomly and use it *under the same coditions* as you used for your 4 bodies, then the MRBF will be some what more conservative. My calculation suggests it is at least 222 rolls. ( based on one-sided Chi-square distribution at 95% confidence level.) If I have the data for R8 I could use what the reliability engineer called time-truncated (without failure) to estimate the MRBF. But for the two sets of data to have any meaningful comparison, the cameras must worked under the same condition (the way you handled them and the environment they were subjected to.) And so far we are assuming the failure rates of the cameras are constant, that is to say the MRBF of first 2 years is the same as that of the subsequent 2 years. It is theoretically acceptable to consider electronic circuits and equipment to have constant failure rate, but rarely so for mechanical parts. You have been using RTS III for 3.25 years but the R8's are less that a year in the market....the discrepancies are there. Cheers, Eng-Suan engsuan@tp.ac.sg (65)780-5532