Defects in quality put a severe dent in the potential profits of companies all over the world year after year. Having an understanding of the total probability of defect puts the power in an organization’s hands to make improvements and reduce the chance of its customers receiving faulty products.Knowing the total probability of defect for your products and processes is a powerful tool for monitoring the health of your organization.

Overview: What is Total Probability of Defect?

You can find the total probability of defect by adding the probability of defect over upper spec limit-p(d), upper with that below lower spec limit-p(d), lower.

2 benefit and 1 drawback of Total Probability of Defect

Here are a couple of benefits of total probability of defect as well as a drawback:

1. Benefit: Risk analysis

Total probability of defect is a vital indicator of the quality of a manufacturing process. It is a powerful tool in an organization’s risk analysis.

2. Benefit: Planning

Having an idea of how often a product will fail allows a company to make the necessary plans to absorb the impact without too much damage to the financial bottom line.

3. Drawback: Difficult with large data amounts

Calculating the total probability of defect in a trustworthy way can be difficult when there is a large amount of data at play.

Why is Total Probability of Defect important to understand?

Total probability of defect is important to understand for the following reasons:


Having a solid understanding of the total probability of defect can help your organization by helping to ensure the highest level of quality possible.


The possibility of a high level of defects is not only an issue of quality but can cause potential safety issues in the workplace. By understanding the total probability of defect, you can make changes that can protect your workers.

Keeping customers

By having a thorough knowledge of the total probability of defects, you can make the necessary changes in quality that can help you retain your customers. Studies have shown that it is statistically more difficult to gain new customers than to keep the ones that you have, so it is important to keep your customer base happy with the quality of the goods and services your organization provides.

An industry example of Total Probability of Defect

A toy company has five potential new products to introduce into the marketplace in time for Christmas. The schedule is tight, so the company has to make a decision soon. Their plan is to pick just one through a thorough analysis of each product to find which is the safest for the public. They will determine this by looking at the total probability of defect for each of the five products and picking the one with the lowest probability.

4 best practices when thinking about Total Probability of Defect

Here are some things to keep in mind when working with total probability of defect:

1. Sources

When determining the total probability of defect, you should consider all possible sources of potential defects. Being thorough in your analysis will provide you with the greatest chance of avoiding defects.

2. Analyzation

Fully analyze the impact of each potential defect.

3. Likelihood

Have a full understanding of the likelihood of each potential type of defect.

4. Consequence

It is a good practice to have a solid comprehension of the consequences of each type of potential defect.

Frequently Asked Questions (FAQ) about Total Probability of Defect

What are some different types of probability in mathematics and statistics?

Three kinds of probability are theoretical probability, experimental probability, and axiomatic probability.

What is the relationship between error, defect, and failure?

It is a sequential relationship in that an error leads to a defect, which then leads to a failure.

Do all defects lead to a failure?

No. Some defects can remain unnoticed, which then will not result in a failure.

Wrangling your total probability of defect

If your total probability of defect is high with a product, it can be a daunting prospect to make the necessary changes needed to increase quality. Not all of the changes need to be made at once, however. You may be in a situation where adjustments can be made bit by bit, focusing on the potential defects that could cause the biggest issues first. Any adjustment made for the benefit of improved quality will make a positive difference. Making further adjustments as you are able will continue to lower the total probability of defect and show your organization’s commitment to continuous improvement.
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