On 6/13/06, James Propp <propp@math.wisc.edu> wrote:
... Another instance of misplaced concreteness is the fiction of an average person, an average family, etc. One can devise a situation in which the average family has four children, but the average child has five siblings! (Posit a three-family house: two of the families have 2 children each, and the third family has 8 children.) Or, say I have two cars, one of which gets 10 miles to the gallon and the other of which gets 40 miles to the gallon. Then my "average car" goes 25 miles on a gallon of gas, but uses 1/16 of a gallon per mile!
Nice material for puzzles and elementary pedagogy, but omits to make a far more practically important point --- there is NO nonuniform distribution of family size for which the average child is a member of the average family! Fred Lunnon