The concept of a sample thus includes the process of how the data are obtained (that is, the random variables). This is necessary so that mathematical statements can be made about the sample and statistics computed from it, such as the sample mean and covariance .
The author of these tools is David A. Schoenfeld, . ( [email protected] ), with support from the Massachusetts General Hospital Mallinckrodt General Clinical Research Center , Research Resources Division, National Institutes of Health, National Center for Advancing Translational Sciences.
Many techniques can be used for either qualitative or quantitative measurements. For instance, suppose an indicator solution changes color in the presence of a metal ion. It could be used as a qualitative test: does the indicator solution change color when a drop of sample is added? It could also be used as a quantitative test, by studying the color of the indicator solution with different concentrations of the metal ion. (This would probably be done using ultraviolet-visible spectroscopy .)
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