This is probably a really easy question but I've got stuck on the last section of question 8, part iii of the Sept 2006 ST3 paper. The Examiners' Report says that "if working in £'s, mean of A is 17.16 & mean of B is 16.22 & mean of total is 17.55". Can someone explain how these figures are calculated from the Normal mean and s.d that are calculated in this question for each of A, B, and the total?
Just do the same calculations as you did to get the 'normal' answer, but this time don't quote figures in millions, just use pounds. Page 14 of the Tables gives you the formulae for the mean and variance of the lognormal distribution with parameters mew and sigmasquared, so solve the simultaneous equations to get the parameters. It doesn't matter which you work in, £ or £m; both would get the marks.
