Life Data Analysis
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Life Data Analysis

Some of the following examples use data sets in an electronic format. These files are located in the "Tutorial" directory on your CD.

### Example 1

Ten units are placed on a test stand.  The following failures were recorded

 Cycles to Fail 283,121 317,982 264,764 451,384 501,236

Of the remaining 5 units, two were removed from testing without failing after 300,000 cycles, and three were removed from testing after 600,000 cycles without failing.

A. Compute the lower 80% confidence limit for reliability at 200,000 cycles.

B. Compute the lower 80% confidence limit for the time to fail at 99% reliability.

Solution

### Example 2

One million units were introduced into the field 6 months ago.  The number of failures per month are shown below.

 Month Ending Number of Failures 1 20 2 28 3 17 4 35 5 12 6 22

What is the expected reliability of the population after 1 year in service?

Solution

### Example 3

Given the data in the file "Demo2.dat",

A. Does the product represented in the data meet a requirement of 99% reliability with 80% confidence at time = 40?

B. At what time does the product meet the requirement of 99% reliability with 80% confidence?

Solution

### Example 4

A new product is required to demonstrate 99% reliability at 1.5 million cycles with 80% confidence.  Given a Weibull shape parameter of 2.8, how long must 8 units be tested to demonstrate the required reliability assuming no failures?

Solution

### Example 5

Nine samples were tested for 3 million cycles without failure, and 1 sample survived 2.84 million cycles before failing.  Given a Weibull shape parameter of 3.8, what is the lower 95% confidence limit for reliability at 2 million cycles?   What is the lower 95% confidence limit for the time to fail when the reliability is 99%?