V. Reliability Testing
C. Product Testing

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

3. Ongoing reliability testing (e.g., sequential probability ratio test [SPRT]) (Evaluate)

Checking for the impact of your supply chain or assembly line variability on field reliability, this is one way to go about doing it.

Additional References

Sequential Sampling by Attributes (article)

Quick Quiz

V. Reliability Testing
C. Product Testing

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

2. Product reliability acceptance testing (PRAT) (Evaluate)

This can be fun, and can be challenging to accomplish.

Additional References

Quick Quiz

V. Reliability Testing
C. Product Testing

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

1. Qualification/demonstration testing (sequential tests, fixed -length tests) (Evaluate)

In some cases we have to be ecumenical with sample size and the testing is pass/fail in nature. Then success testing is the way to go. Plus, it is a great tool to estimate sample sizes for testing.

Additional References

Sample Size – success testing (article)

Extended Bogey Testing (article)

Quick Quiz

1-134. A unit is designed to achieve 96% reliability at a 90% confidence level. Which of the following is the minimum sample testing results that reflects the requirements?

(A) 200 units to be tested with one failure reported
(B) 100 units to be tested with one failure reported
(C) 50 units to be tested with no failures reported
(D) 25 units to be tested with no failures reported

V. Reliability Testing
C. Product Testing

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

1. Qualification/demonstration testing (sequential tests, fixed -length tests) (Evaluate)

At times our product expected lifetimes is relatively short and running the product in realtime can be a form of reliability test.

Additional References

Sequential Sampling by Attributes (article)

Quick Quiz

Additional References

Quick Quiz

1-44. You need to verify that the maintainability requirement of a design is being met. What is the most accurate method to do so.

(A) Analyze the design.
(B) Perform maintainability prediction.
(C) Conduct thorough design reviews.
(D) Conduct a demonstration at the customer’s facility.

V. Reliability Testing
B. Testing during development

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

4. Software testing (e.g., white-box, black-box, operational profile, and fault-injection) (Evaluate)

Software continues to delivery more functionality for even simple systems.

Additional References

Quick Quiz

1-54. Identify which models are used for software reliability,

I.   basic execution time model

II.  simulation model

III. Markov analysis model

IV.  logarithmic Poisson execution time model

(A) I and II only
(B) I and IV only
(C) II and III only
(D) I, II, III, and IV

V. Reliability Testing
B. Testing during development

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

3. Reliability growth testing (e.g., test, analyze, and fix (TAAF), Duane) (Evaluate)

Especially useful for large complex systems, we can track the trajectory of the incremental improvements.

Additional References

SOR 050 Implementing System Reliability Growth (podcast)

9 Reliability Growth Patterns for Two Test Phases (article)

Reliability Growth Testing (article)

Duane Plot of Cumulative Failures Over Time (article)

Quick Quiz

1-136. Identify the important steps in the planning and conduct of a test, analyze, and fix program.

I.   Fully analyze all failures.
II.  Accept some failures as non relevant.
III. Dismiss no failure as random.
IV.  Take corrective action on all failures.

(A) I and IV only
(B) II and III only
(C) I, III and IV only
(D) I, II, III, and IV

V. Reliability Testing
B. Testing during development

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

2. Discovery testing (e.g., HALT, margin tests, sample size of 1) (Evaluate)

Sometimes we just need to know what will fail in order to improve a design or system.

Additional References

Discovery Testing (article)

Why HALT is a methodology, not equipment (article)

Quick Quiz

V. Reliability Testing
B. Testing during development

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

1. Accelerated life tests (e.g., single-stress, multiple-stress, sequential stress, step-stress) (Evaluate)

Build, conduct, and interpret accelerated testing takes more knowledge than briefly covered here.

Additional References

SOR 036 Selecting the Correct Acceleration Test Model (podcast)

SOR 035 Introduction to Acceleration Models (podcast)

Norris Landberg solder joint fatigue (article)

Lead Free Solder Accelerated Testing (article)

V. Reliability Testing
B. Testing during development

Describe the purpose, advantages, and limitations of each of the following types of tests, and use common models to develop test plans, evaluate risks, and interpret test results.

1. Accelerated life tests (e.g., single-stress, multiple-stress, sequential stress, step-stress) (Evaluate)

Build, conduct, and interpret accelerated testing takes more knowledge than briefly covered here.

Additional References

Select the Right Accelerated Life Test Approach (recorded webinar)

Accelerated life testing first steps (article)

Life Testing Starting Point (article)

Quick Quiz

1-132. Accelerated cycling is performed on a sample of devices for six months under normal operating conditions. What can be gained by a cycling program?

(A) It can reduce premature failures in use.
(B) It can reduce the constant failure rate probability.
(C) It can ensure acceptable customer quality.
(D) It can discover all failure mechanisms.

1-137. An expensive mechanical part needs to be evaluated to determine its adherence to design requirements. Why would accelerated life testing be conducted on such a part?

(A) because test to provide adequate reliability performance information under normal operating conditions would take too long
(B) because the error in the population resulting from part-to-part variation is too large
(C) because the probability density function of the product follows either a lognormal or a Weibull distribution
(D) because the current sample size and the life distribution indicate that wear-out is likely

V. Reliability Testing
A. Reliability test planning

2. Test environment (Evaluate)

Evaluate the environment in terms of system location and operational conditions to determine the most appropriate reliability test.

Understanding the where and how of product use permits adopting test conditions that reflect or accelerate use conditions correctly.

Additional References

The Environmental Test Manual (article)

SOR 062 Are Environmental Standards Useful? (podcast)

SOR 059 How to Set Environmental Specifications for Testing (podcast)

SOR 043 Environmental Testing and Reliability (podcast)

Is Environmental Testing Part of Product Reliability? (article)

Create a Meaningful Environmental Test Plan (recorded webinar)

Quick Quiz

1-139. A sample of 25 mechanical parts is subjected to a 5-week stress test in which each part is subjected to a load stress that increases 50% each week. The test results are listed in the table.

Week                     Number of failures

1                                  0

2                                  1

3                                  1

4                                  3

5                                  7

You need to determine whether the failures observed reflect actual use failures. What additional information do you need?

(A) the times of the failures
(B) the history of cumulative stress
(C) the geometry of the test setup
(D) the mechanisms of the failures

V. Reliability Testing
A. Reliability test planning

1. Reliability test strategies (Create)

Create and apply the appropriate test strategies (e.g., truncation, test-to-failure, degradation) for various product development phases.

In this lesson the focus is on human factors testing.

Additional References

Quick Quiz