sample variance vs. population variance

Question from Schweser: The population’s mean is 30 and the mean of a sample of size 100 is 28.5. The variance of the sample is 25. The standard error of the sample mean is closest to: A. 0.05 B. 0.25 C. 0.50 D. 2.50

annasmom, STD = sqrt(variance) STD = sqrt(25) = 5 S.E. = STD/ Sqrt(n) SE = 5/ sqrt(100) SE = 5/10 SE = 0.5 Would bubble-in ‘C’ - Dinesh S

Yes, the correct answer is C. I understand that we’re supposed to use the sample standard deviation to estimate the standard error of the sample mean when the population standard deviation is not known. In the Schweser Notes, they indicate that “The standard error of the sample mean is the standard deviation of the distribution of the sample means.” I think I was confusing the “sample standard deviation” which refers to a single sample, with the “standard deviation of the the distribution of the sample means.”