Not only does the graph correct the small experimental errors in the evidence, but it also is useful for making quantitative predictions. You should be aware, however, that the line, while probably more accurate than the original data table, is far from perfect, and becomes less reliable the further you travel on it from the region in which data were collected. But we are not done. While graphs cannot be combined, equations of graphs can. The next step is, if possible, to determine the equation of the line or curve from the graph.
Equations are like building blocks.
They can be algebraically combined with each other to give more and more complicated, multidimensional models of reality. Experimenting in the physical sciences, then, involves taking a complex world and identifying or inventing relevant variables. We then attempt to control these variables so that only two may change so that we may easily discover the equation that relates these variables. One by one, we perform new experiments, adding new variables to the equation, in an attempt to rebuild the complex world that we began with, only in mathematical terms. When scientists invent abstract variables such as pressure, volume, moles, and temperature, as solutions to various measuring instruments, scientists are acting in ways parallel to some modern abstract artists in inventing symbols.