Quality is a much broader aspect than Reliability. Quality covers almost everything from organisation, managements, service, procedures, people, product, product-life etc. In simple words, Reliability is only a subset of quality, the others being performance, consistency, efficiency, user experience etc. Whereas, Quality is the measure of conformance to laid down product specification. Not understood? Tricky language. Isn’t it? If you have to read such a tricky language, then you can get it from books also. Then, why to come on-board this web-blog. Don’t you worry. Let’s simplify it to understand the difference between Quality and Reliability.
We will take an example: Suppose, you went to a shop to buy oranges. If the orange is good or bad, that measure is quality. You took the oranges that day and returned to home. Next day you again visited the same shop to buy oranges and found that the oranges available there are good again. You purchased it and returned to your home. You repeated the same process for one week and every time you got good oranges. Now, you have a trust on that shop that you will always get good oranges there, and that’s Reliability.
Now we can say that:
- Quality is Present (today) while Reliability is the future.
- Quality can be controlled and measured to the accuracy, while Reliability is just a probability. We can ensure reliability by controlling the quality.
- Quality is every thing untill put into operation (i.e t=0 hrs), while Reliability is every thing that happens after t=0 hrs.
In other words,
Product’s quality is measured prior to customer’s initial product use. However the Product reliability is measured during/after the customer’s product use.
- Quality is the measure of conformance to laid down product specification.
- Quality is a static measure of product meeting its specification, whereas Reliability is a dynamic measure of product performance.
- Quality is observed whereas reliability is experienced.
- You buy based upon quality. You come back and buy again based upon reliability
- Poor quality system can have better reliability and a good quality system can have poor reliability.
- Once design is over, maximum system reliability is fixed and through quality assurance what we can achieve is design reliability.
- Quality is one among many parameters to ensure better reliability.