How to Select X-axis Values when the Independent Variable Spans Several Orders of Magnitude

When designing experiments, researchers often need to measure a dependent variable, such as the response of an instrument or method, with respect to an independent variable such as the concentration of a reactant. Often the independent variable spans several orders of magnitude, (e.g., when experimental concentrations range from 0.0100mM to 10.0mM), which can make it difficult to construct a clear graph of the data. In such situations, it is more appropriate to plot the independent variable on a logarithmic axis (usually the base 10 logarithmic scale) rather than a linear axis, in order to avoid superimposed data points and to make the graph easier to interpret. By convention, the independent variable is usually plotted horizontally as the x-axis or abscissa, and the dependent variable is plotted vertically as the y-axis or ordinate.