Help!! I am doing my stat homework and I got stuck with this question " A study is made of the age at entrance of college freshman. Is the SD about 1...

Help!! I am doing my stat homework and I got stuck with this question " A study is made of the age at entrance of college freshman. Is the SD about 1 month, 1 year, or 5 years. Why? Please help out a fellow student here and I need clear calculations on why..