Figure 11 Age-adjusted lung cancer rates are plotted vs. radon levels in counties in the study data base. Age-adjusted lung cancer rates are plotted vs. radon levels in counties in the study data base. The abscissa is divided into ranges shown at the top which also shows the number of counties in each range. Lung cancer rates for each set of counties are plotted along with mean, standard deviation, and first and third quartiles. Least squares best fit lines are plotted for the mean values. (42)