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Started by Pierre Dupont
Wed, 28 Aug 2002 16:44
frequency and specification
Author: Pierre Dupont
Date: Wed, 28 Aug 2002 16:44
Date: Wed, 28 Aug 2002 16:44
50 lines
2343 bytes
2343 bytes
The data : - A temporal serie : (x1, x2, ., xn) - Time between two observations : delta - specification : X < b How i can change delta to be able to react enough early to not have a point out of the specification? Intuitively, if I increase the frequency , i can react more quickly. But. Formelly Hypothesis : random observations The variable X has a mean m and a standard deviation sigma. Notations : X = variable delta = time between two consecutive observations lambda = failure parameter L = lenght before OS (Out of Specification) The expectation of L is: 1/p where p=P(X>b). For simplicity, I suppose that the only failure is a shift of the mean where the mean pass from m0 to m1 = m + lambda* sigma. The average time before an OS if no failure (lambda = 0) is : Delta * E0(L). For a failure lambda, the average time before an OS is: Delta * E(L;lambda). If the frequency change from Delta to Delta1 = c* Delta, the average time before an OS is :Delta1* E(L;lambda) = c *Delta* E(L;lambda). If the variable has a large deviation, or is too close of the specification, the average time before an OS is little. So, intuitively, I increase the frequency of the observations. But the observations are independent, so the average length before an OS is constant and the average time before an OS decreases ! Where is the bug ?
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