[802.3_OMEGA] Calculating hazard rate (statistical aspects)
The following is a description of the statistical aspects of calculating the hazard rate. We don't need to spend time on this at
the meeting.
Ruben has presented a Matlab code for doing the simulation on the reflector. The important thing to appreciate is that only statistical
averages are relevant.
1) The automotive mission profile shows the probability of a vehicle being at each of five different temperatures. Each vehicle may take
a different path through the temperature profile.
2) Hazard rate h(t) is meaningful only as a statistical average ⟨h(t)⟩ because the goal is to estimate the failure rate of an ensemble (fleet)
of vehicles.
3) A Monte Carlo simulation can be used to simulate temperature history and determine ⟨h(t)⟩. The simulation should be run
many times and ⟨𝐡(𝐭)⟩ determined by taking the average. Spikes in h(t) for a brief time in any one Monte Carlo run do not carry
much meaning by themselves because it is the resulting failures that count, not the value of h(t) itself. The resulting failures
depend on ⟨h(t)⟩.
4) Alternatively, de-rating the hazard rate at EOL by the fraction of time at each of the five temperatures will give the same value
of ⟨h(t)⟩ as the Monte Carlo simulation.
Ramana Murty
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