I am not able to understand the normal distribution for the sample mean. The formula says that X(bar) ~ N(mu, sigma^2/n) but here neither standard deviation(sigma) is squared nor divided by the sample mean number which is given as 10 Reply ASAP !!
I think it might look that way, but in fact the SD of X bar is 10^2 divided by n of 10, which is 10! Also, the SD of Y bar is 5^2 divided by n of 5, which is 5!
But if you look at the exam style question of Chapter-9, i guess there is no difference between that and this question. M still not able to understand what you are trying to explain.
Hi Just follow this logic ... sigma = SD(X) = 10 Var(X_bar) = sigma^2 / n = 10^2 / 10 = 10 So, X_bar ~ N(100, 10)
But they are working in thousands....so if you square 10,000 n den divide by 10 then the answer is not 10,000.
If you work in units rather than thousands, the variance of X bar is 10,000^2/10 and the SD of X bar is 3,162.2776. Working in thousands, the variance of X bar is 10^2/10 and the SD of X bar is 3.162.
i still don't get it ! it means that the solution is wrong coz it is one of the easiest questions and has been done several times in the core reading but differently here.
