Do this to select a column name for every open field on the panel. That column name will now be in your field. Highlight the column you want to use for the selected field, then drop just below the window listing all columns and click on the Select button. This will cause all available columns that are not already assigned to be shown in the window on the left. If you are not familiar with Minitab, the way to select a column for one of their entry fields is to first place your cursor in the field. Be sure to select which of the entries is considered good in the “Value of good or acceptable items” window. You will need to tell Minitab which columns are your appraiser names, your item numbers and of course your data. If you used Minitab to set up the study, the form it created will be organized for easy analysis. One limitation within Minitab, is that it almost always requires the information to be in columns not rows. The Minitab workbook operates similar to an Excel spreadsheet – in fact you can directly copy and paste data form one application to the other. This panel will ask where information is found in your Minitab workbook. When selecting the analysis side for attribute data, a second panel is displayed. When setting up the study, you will need to provide the true status for each item in order for Minitab to create the Reference Standard column. Whichever path you choose, you then have two options, either to set up the study which will create the data collection form for you, or the analysis side which will perform the calculations. Attribute data analysis is on the right side of the first diamond and is labelled "appraisal". When selecting Measurement Systems Analysis the wizard panel shown below appears. Minitab provides a wizard for measurement systems analysis that is found under the "Assistant" pull down menu. The system effectiveness is the number of times that all appraisers agreed on all trials with each other and the reference standard for an item divided by the number of items and that converted to a percentage. Appraiser #1 = 2 occurrences, Appraiser #2 = 1 occurrence, Appraiser #3 = 0 occurrences. Appraiser #1 = 2 occurrences, Appraiser #2 = 4 occurrences, Appraiser #3 = 2 occurrencesįalse Alarm Rate is based upon the Appraiser assessing a “Fail” for what should be a “Pass.” The False Alarm Rate is the number of times that occurred divided by the number of assessments of units whose true status was “Pass” and that converted to a percentage. The Miss Rate is based upon the Appraiser assessing a “Pass” for what should be a “Fail.” The Miss Rate is the number of times that occurred divided by the number of assessments of units whose true status was “Fail” and then converted to a percentage. Appraiser #3 – first pass = 24 times, – second pass 24 times. Appraiser #2 – first pass = 22 times, – second pass 23 times. Appraiser #1 – first pass = 24 times, – second pass 22 times. First is the measure of accuracy, which is the number of times that each appraiser correctly assessed the item value divided by the total number of inspections and then converted to a percentage. The accuracy measures will include the use of the Reference Standard column in the comparisons. Reproducibility is the calculation of the number of times all Appraiser #1 = all Appraiser #2, all Appraiser #1 = all Appraiser #3, and all Appraiser #2 = all Appraiser #3 divided by three times the number of items and then converted to a percentage. The System Repeatability is the average of those three: (92% + 88% + 100%)/3 = 93.3% This is done by determining the number of times an appraiser is consistent in their evaluation (which is the match column) divided by the number of items, and then converted to a percentage. Repeatability calculations are first conducted at the individual level first. It is for a study with three Appraisers, 25 items, and two trials. This example will be based upon the data set shown below. When doing your first few Gage R&R Studies, you will want to refer to the example to guide you through the process. MINITAB 18 WORKBOOK SOFTWARE
The same example is then demonstrated the statistical software program Minitab, which is often used to conduct analyses for Lean Six Sigma projects. This example is demonstrated using comparison equations with a spreadsheet in Microsoft Excel. An example of an attribute data Gage R&R analysis will illustrate the power of the technique.
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