Before your analysis, take these steps: Assuring accuracy in data collection

Matt SavageTrue or false: Collecting data, unlike other processes, is not subject to variation.

Well, of course this statement is false. Variation is inherent to any system, and excessive variation in the collection process can provide highly misleading analysis, since it will appear on control charts as variation in the process, potentially skewing the outcome and inhibiting accurate analysis.

Collecting data with measurement instruments such as gages or calipers demands the use of repeatability and reproducibility (R&R) tests in order to assure that the collection will be accurate. Repeatability is the variation found in a series of measurements that have been taken by one person using one gage to measure one characteristic. Reproducibility represents the variation in a series of measurements that have been taken by different people using the same gage to measure one characteristic of an item.

Gage R&R tests are critical to assuring consistency and accuracy in collection of data using measurement equipment. Setting up regular gage R&R testing prevents both calibrating gages that don’t need it and failing to calibrate those that do.

R&R studies address two major causes of variation in measurement systems: gage variability and operator variability. Gages may be subject to factors such as temperature or magnetic and electrical fields that may affect their accuracy. Operator variability is caused by different interpretations of a vague operational definition or differences in background, fatigue, or even attitude of operators.

Knowing how to conduct R&R studies and interpret them are critical to measurement accuracy. Get help with these subjects and access to a series of frequently asked questions about gage R&R.