abcdef12345678

[img][/img] [img][/img]question 12/(c)(ii)in the marking scheme the standard deviation used is 0.8, but a sample of 20 is drawn, so why the standard deviation is not 0.8/(20)^(1/2)  既係why not (8 / square root 20) ?

[ 本帖最後由 abcdef12345678 於 2014-3-14 12:08 AM 編輯 ]