Selected baseline characteristics of cases and controls,1 Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study.

1All values are medians and interquartile ranges unless otherwise indicated as percentages.2P-values are based on Chi-square tests (for categorical variables) and Wilcoxon rank sum tests (for continuous variables).3Median values for number of cigarettes per day are identical because 31% of subjects reported smoking a pack of cigarettes/day ( = 20), however, the overall distributions by case/control status differ, as is evident by the interquartile ranges and the p-value.4Family history data available for 67.6% of subjects.5Dietary data available for 94.2% of subjects.6Only 21.2% of subjects reported any supplement use.