Finding the Standard Error of a Sampling Distribution Don't forget. According to the CLT, the standard error (aka standard deviation) is about or sometimes Vn S Vn We are interested in developing a sampling distribution for the average time Olympic marathon runners complete a marathon in. This is based on the 2012 Men's Olympic Marathon which had 85 finishers. Data is available at StatKey , select Sampling Distribution for a Mean , then change the data set to Olympic Marathon-Ze (Minutes). Summary Statistics Population size Mean StDev Median 85 140.592 8.007 139 For samples size of n = 30 use the standard error formula or create a sampling distribution by running at least 6000 samples based on their data set. The standard deviation for the population is The standard error for the distribution of sample means from samples of size 30 is Question Help: Message instructor