## The Basic Practice of Statistics 7th Edition

Marginal distribution is the sum of counts of each column divided by sample size of 19558 18 to 24 years =$\frac{6432+5640}{19558} = 0.6172 = 61.72%$ 24 to 34 years = $\frac{2450+1843}{19558} = 0.2195 = 21.95%$ 35 years or older = $\frac{2124+1069}{19558} = 0.1633 = 16.33%$ From this we can deduce that 61.72% of undergraduates are in the age bracket 18 - 24 years