Introduction

Measurement systems are essential to the quality of a manufacturing process. The gages or instruments that take measurements are subject to variation. Too much variation in the measurement system may mask variation in the process.

One type of measurement variation is caused by conditions inherent in gages. This variation, known as repeatability, is obtained when one person measures the same characteristic several times with the same gage. Another type of measurement variation, known as reproducibility, occurs when different individuals measure the same characteristic with the same gage. Other sources of measurement variation include part-to-part variation, accuracy, stability, and linearity.

Two graphical methods for evaluating the measurement system are range charts and average charts. Range charts assess repeatability by showing whether the gage variability is consistent. Average charts show consistency of operator variability (reproducibility) and part-to-part variation.

Two statistical approaches to determining gage R&R are the average and range method and the variance components method. The variance components method can provide more information, is more accurate, and is more flexible than the average and range method.

The GAGE application makes it easy for you to enter your data, create range and average charts, and determine gage R&R. Whether you use the average and range method or the more powerful variance components method, the GAGE application reports the results in a standard form. It enables you to save the graphs for later reference, and it enables you to save the reports. You can save the data in a SAS data set for subsequent gage analysis or for more extensive analysis using other components of the SAS System. Because gage R&R techniques are open to local interpretation, this application has been designed so that it can be modified to suit the needs of your company.