Lai Wei-hsiang
Plant 3
The end of shift bell rings. Tom of the Quality Assurance Department is feeling relaxed and getting ready to leave work. He runs into Jay in the Technical Divsion at the door.
Jay: Wow, are you leaving now? Don't you have to work overtime today? Didn't you always have to work overtime until seven or eight in the evening before you could leave?
Wei: Haha! I am in luck! Since we bought the NIR (Near Infrared Spectrometer), the inspection time for raw materials and products has been greatly reduced. In the past, we needed to wait for an hour before we could see the results of the test. Now we only need to wait fifteen minutes!
Comparing the new equipment with the old one
Jay: Wow, that's amazing! Fifteen minutes is all you need to know the results. Then, is data reliable?
Wei: Of course, no problems! We intentionally used statistical analysis to calculate its GRR and it is less than 2%! This shows that its test results are very reliable!
Jay: Then, do you know the difference between older testing methods, like Gas Chromatography, and the new method, Near Infrared Spectrometer?
Wei: We do! That is definitely necessary! We applied statistical analysis on the results of these two methods and proved that the variance and mean of the testing figures of these two instruments are no significant difference. In other words, the testing results of these two instruments are equivalent.
Jay: Wow, you are full of professionalism!
Wei: The more important issue is that the reduced inspection time greatly shortens the wait time. It helps to eliminate the production bottleneck for the plant because the production unit can now make the decision faster determining whether the reaction has completed to go to the next step.
Critical decision-making by analytical evidence
Wei: Actually, this could happen only because statistical tools are doing us a big favor! In the introduction of new equipment, new methods, and new material, we can employ the assistance of statistical techniques and help us analyze whether the testing capability of a piece of equipment is sufficient, whether it is stable, and whether there are differences between the two. With the results of statistical analysis, when managers and owners are making the decision, they can feel more assured and have few things to worry about. We must invest on the right equipment, otherwise it will be a great deal of loss to the company if wrong interpretations are made in terms of quality and process.
Jay: As I listen to your story, I now know that the statistics are very useful. I also need to bring this matter to the attention of the supervisor of our unit and see if we can find equipment or operational methods that are timesaving, laborsaving, and efficient, by using statistics. We can work together to improve the efficiency and create a happy work environment!
Wei: You're absolutely right! We will support and encourage each other!
Paired test & GRR
1.How can we be sure of the consistency of two testing methods or two instruments?
We can use “paired test.” The method is as follows:
1). The same object is tested separately under two testing methods or two instruments.2.GRR(Gage R&R): It is a comprehensive indicator that measures precision of measurement system. Its meaning is gage repeatability and reproducibility of the operating condition. It is derived from variable analysis and estimate. When GRR<10%, it means that the measurement capability is good. When GRR is between 10% and 30%, it means that the measurement capability is acceptable. When GRR>30%, it means that the measurement capability is poor and requires immediate improvement.
2).We calculate the difference between the numbers under the two testing methods or twoinstruments of each object tested and examine whether the difference is significant.
3).If the difference is significant, it shows that the test results from the two testing methods or two instruments are different.
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