# Validating destructive test methods

For example, suppose you are measuring the hardness of a steel bar and would like to do a Gage R&R on the hardness tester. You can cut the bar into 10 pieces to be tested for hardness. Suppose you have three operators and you want each operator to test two pieces per batch. So, you have enough pieces for each operator to test pieces from each batch. Now suppose you were using 6 operators and wanted each operator to test 2 pieces per batch.

Are there enough parts in each batch so that each operator in the study can run at least two parts from each batch?

The experimental layout is shown below in Figure 2. It is a measure how close the operator is to getting the same result each time he measures the same part.

Figure 2: Crossed Gage R&R for Non-Destructive Measurement System Figure 2 shows the 2 trials for part 1 that Operator 1 runs. Each set of trials for each part, under each operator, gives another estimate of the repeatability.

Since there are not enough pieces per batch, you will have to setup the design so each operator measures 2 pieces from a unique batch (bar). For example, if you are measuring the length of a part, that part is not changed during the measurement.

To perform a non-destructive gage R&R, you must decide on the following for the study: For example, you may decide to use 2 operators, 3 parts and 2 trials.