ACME Example

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ACME manufacturing has implemented an accelerated life testing program for their new product design. A total of 40 units were tested at four different pressure levels. The operating stress level is 170 psi. The following table shows the data from the test. Determine the parameters of the inverse power law Weibull model and obtain the use level probability plot with 90% 2-sided confidence bounds on time.


Stress Level, psi 220 psi 230 psi 240 psi 250 psi
165937226
1771067344
2381569963
29017012468
Times-to-failure, hr32018513469
34021415072
34122018277
38023618696
449252190131
544288228140


The parameters of the IPL-Weibull model are estimated to be:


\begin{align}

  \beta =\ & 3.009236 \\ 

  K=\ & 3.267923E-27 \\ 

  n=\ & 10.218104  

 \end{align}


The use level probability plot is shown next.


The probability plot at a use stress level.


In ALTA, the confidence bounds on time are the Type 1 bounds (Time Bounds).


The probability plot at a use stress level with 90% Type I confidence bounds.
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