Gage R & R Studies
Can I trust my measurements?
You might take for granted that when you measure something, you get the right answer. But if you follow the adage "measure twice, cut once," you've probably found out that this isn't always the case.
While no measurement system is perfect, we rely on them to collect data to control quality and monitor changes in critical processes. So how do you know if the changes you see are real, and not just the product of a faulty measurement system? After all, if you can't trust your measurement system, then you shouldn't trust the data it produces.
Minitab's gage R&R study can help you identify problems with your measurement system, allowing you to trust your data and affect real improvements in your business processes.
What can gage R&R do for you?
Gage R&R studies can tell you if inconsistencies in your measurements are too large to ignore—whether due to a faulty tool or to inconsistent operation of a tool.
Reveal an inconsistent toolIn preparation for using a control chart to monitor the fill weights of cereal boxes, a company conducts a gage R&R study. The results show that even when the same person weighs the same box on the same scale, the measurements can differ by several grams, indicating the scale is in serious need of recalibration. The faulty scale would have rendered the control chart virtually useless. | 
| | Although the average measurements are not far apart, the spread of the measurements is huge! |
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Highlight operator differencesTo meet increased demand, a company hires new workers to prepare carefully-measured amounts of a costly solution. The company uses a gage R&R study to compare the new operators to more experienced operators. The study reveals that when workers measure the same sample, the measurements of new hires are too high or too low more often than the measurements of experienced workers. The company decides to conduct more training for the new hires. |  | | The measurements of the new hires do not agree with the measurements of more experienced operators. |
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How to analyze a gage R&R study in Minitab
Awareness of how well you can measure something can have substantial economic benefits. Minitab makes it easy to analyze how precise your measurements are. A restaurant plans to evaluate how it measures food temperature to ensure it's hot enough. Inaccurate temperatures can result in discarding food that was safe, failing a health inspection, or even making a customer ill. | |  | | Reproduced With Permission |
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Getting started
Preparing to analyze your measurement system is easy because Minitab's Create Gage R&R Study Worksheet can generate a data collection sheet for you. The dialog box lets you quickly specify who is taking the measurements (operators), which item they are measuring (parts), and in what order the data should be collected.
- Choose Stat > Quality Tools > Gage Study > Create Gage R&R Study Worksheet.
- Specify the number of parts, number of operators, and the number of times the same operator will measure the same part, then give descriptive names to the parts and operators so they're easy to identify in the output. Click OK.
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The main event
After entering the measurements in the prepared worksheet, you're ready to use Gage R&R Study (Crossed) to analyze the measurements.
- Choose Stat > Quality Tools > Gage Study > Gage R&R Study (Crossed).
- In Part Numbers, enter Parts.
- In Operators, enter Operators.
- In Measurement Data, enter 'Food Temp'.
- Click Options and enter your specification limits; in this case, enter a lower specification for the minimum food temperature. Click OK in each dialog box.
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The study reveals that Morgan's measurements are lower than Taylor's or Robin's. Identifying and eliminating the source of the difference will improve the measurement system. Morgan, Taylor, and Robin suggest that the hardest part of measuring soup temperature consistently is measuring soup from the same depth in the pot, so markings are added to ladle handles to make depth easy to determine. |  | | The difference between Morgan and the others indicates improvement is possible. |
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Putting gage R&R studies to use
It's easy to forget that taking measurements is like any other process—prone to variability. Taking steps to reduce this variation with Minitab's gage R&R tools ensures you can trust your measurements. The addition of the Create Gage R&R Worksheet tool makes evaluating your measurement system easier than ever.
When you evaluate your measurement system, you can have confidence you're getting data you can trust.