I'd be really unhappy if this sort of question came up in the exam - it's mathematically incorrect. From the way that the question was asked, and the way the solution is drawn up, it is effectively assumed that the following holds:
E[log X] = log (E[X])
Which, since X is not constant, it doesn't! You could only possibly answer this question by assuming N of the form suggested, rather than E[N], and Y of the form suggested, rather than E[Y], which I guess is what the Revision Note solution was trying for?
Last edited by a moderator: Apr 20, 2007