Question: A local authority housing stock consists of three types of house construction; X, Y and Z, comprising 54%, 28% and 18% respectively. An inspection of the housing stock revealed the following proportions of properties with serious structural problems:

X Y Z

% s.s. problems 21% 15% 32%

a) What proportion of the whole housing stock has serious structural problems? [2 marks]

b) If a house is known to be sound what are the chances that it is of type X, Y or Z? [2 marks]