21. When asked by the National Opinion Research Center "Is there any area right around here that is, within a mile-where you would be afraid to walk alone at night"", in 1973 60% of females answered yes and 20% of males answered yes, whereas in 1994 60% of females answered yes and 30% of males answered yes.

a) Calculate the odds that a female responded yes in (i) 1973. (ii) 1994. Interpret.

b) Calculate the odds that a male responded yes (i) in 1973, (ii) in 1994.

c) Calculate the odds ratio between gender and response, in 1973 and in 1994. In winch year is the association stronger?