![]() ![]() But such a calculation is somewhat cumbersome unless you use a computer program. Then, pool all 10 values and compute a single standard deviation. Now that we have our data how do we compute repeatability? One way to do so is to compute the standard deviation for each of the 10 parts in this study. This is the definition of repeatability and we say that we have r=2 trials for each part where “r” represents the number of values. Each number, for a part, represents a value for the same feature, from the same gage measured by the same person. Let’s examine the data in the table above. The data in the table represent two values for the same part feature measured twice by the same operator using the same gage. Once the operator completes their measurements they repeat the process again. Each operator measures a specific feature of a part that’s presented randomly and records a value. The Quality Engineer conducting the study presents the sample to two lab operators. The parts represent the typical variation exhibited by the process. Here we show ten parts selected at random from a process. In this post, lets consider the following data set. Step 1: How to Calculate Gage Repeatability – Collect the Data The Average and Range method does not take this interaction in consideration. The ANOVA method accounts for the interaction between the operator and the parts measured. It is the method most often used, but inferior to the ANOVA method. We will be discussing the Average and Range method. In conducting a Gage RR there are two methods the MSA manual refers to they are the Average and Range and ANOVA methods. ![]() Many consider this manual an authoritative source in conducting a Measurement Systems analysis. The Automotive industry Action Group (AIAG) publishes a Measurement System Analysis (MSA) manual. Reproducibility is the variation in the average of values made by different operators using the same measuring instrument when measuring the identical feature on the same parts. Repeatability is the variation in values obtained with one measuring instrument when used several times by an operator while measuring the identical feature on the same part. When someone refers to a Gage R&R (Gage RR) they’re referring to Repeatability and Reproducibility. ![]() The best place to start is with a couple of definitions. In this post we’ll discuss how to calculate Gage Repeatability using the average range. Over the next few weeks I plan to roll out a number of posts I trust will enlighten everyone. So I decided to write several posts about the topic. I’m often asked to help Quality Engineers better understand how to perform Gage R&R calculations. How to Calculate Gage Repeatability How to Calculate Gage Repeatability Using the Average Range. ![]()
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January 2023
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