How do you derive the result for classical credibility Z =(n/n_s)^0.5 I have done this for n_N and n_x but can't derive it for n_s.
I suspect this is not the optimal use of your time. The harder you have to search for a proof online, the less likely it is the examiners will be interested in it. (Never say never though, of course.) If you really fancy a bit of light bed-time reading, a brief explanation is given at the link below. See footnote 17 on page 8-32. https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwiZoa2ttubLAhUL2BoKHcSjBDQQFggcMAA&url=https://www.soa.org/files/pdf/C-21-01.pdf&usg=AFQjCNEMEJFgNqj3L4a8UOXWdjb4YEDXcg&sig2=gYrpptrhi7MXKY7anrzr7A
