The control chart data analysis approach is an ideal method to evaluate the quality of test data using a specific tester, such as a microindentation hardness tester, over a period of usage time with the same certified test block and indenter. The method described in ASTM E2554, Standard Practice for Estimating and Monitoring the Uncertainty of Test Results of a Test Method Using Control Chart Techniques, was used for this work. This analysis is done by plotting a means and a standard deviation control chart of the weekly or periodic verification data obtained with a certified hardness test block at a specific test force and a specific hardness level. The method is first illustrated using a Knoop hardness test block certified at a test force of 500 gf and with a long diagonal length of 116.18 μm (527.1 HK). From this data, one can easily calculate the uncertainty of the measurements. The second example is for a 300-gf Knoop test block with a certified long diagonal length of 154.5 μm (178.8 HK). Different problems were encountered during the use of each test block, which are readily detected using the control chart method plots.