In an experimental study, good measurement systems are important for approaching successful decisions. The assessment of a measurement system is known as "Gage Repeatability and Reproducibility" (GR&R). "Measurement System Analysis" (MSA) should be performed at the beginning of an experimental study to ensure that the information to be collected are true representation of what is occurring in the experiment. Experimental data collected under the same condition usually show variation, which arises partly from the experimental system, partly from the measurement devices and partly from the operator who makes the measurements. MSA helps to differentiate the contribution of each source to the randomness of the data. In this way, one may see whether there is a need to reduce the measurement variation so that the data reflects basically the experimental variation. Besides, MSA gives quantitative measures for repeatability and reproducibility. Repeatability is the variation in repeated measurements taken by the same operator under the same experimental conditions. Reproducibility is the variation in data obtained by different operators taking the measurement with the same setup under the same conditions. These are measures of the consistency and precision of the data.