Count data

Counts are non-negative whole numbers and they depend on how big the group is, which is why comparing raw counts across groups of different sizes misleads. For example, 45 walkers in a 300-student school is a larger share than 60 walkers in a 600-student school, since $45 / 300 = 0.15$ beats $60 / 600 = 0.10$. Converting each count to a proportion or a rate is the fix. Counts are also what chi-square procedures require, because the test compares observed counts to expected counts; entering percentages instead produces a meaningless statistic.