Use categorized quantile-quantile plots to visually check for the fit of a theoretical distribution to the observed data by examining each quantile-quantile (or Q-Q) plot for the respective level of the grouping variable (or user-defined subset of data).

In a Q-Q plot, the observed values of a variable are plotted against the theoretical quantiles. When the plotted values fall onto a straight line, a good fit of the theoretical distribution to the observed values is indicated. One component graph is produced for each level of the grouping variable (or user-defined subset of data), and all the component graphs are arranged in one display to allow for comparisons between the subsets of data (categories).

See also, Quantile-Quantile Plots and Graphs - Categorized Quantile-Quantile Plots.