Solution
= Solution
By symmetry, each student in the university has probability $(S/N)(1/S)=1/N$ of being in the college and then selected. Hence the <prior probability> is
$$
\boxed{P(\text{lazy})=L/N.}
$$
= Solution
By symmetry, each student in the university has probability $(S/N)(1/S)=1/N$ of being in the college and then selected. Hence the <prior probability> is
$$
\boxed{P(\text{lazy})=L/N.}
$$