How to Find the standard error of the mean

In this video the tutor explains about the standard error of the mean. He starts explaining by drawing the diagram of a distribution and now he takes ten samples from the distribution and starts plotting them. He says that in theory if we do it infinite times then we can obtain the sampling distribution of the sampling mean. For the example he takes the number of samples as 10. Now depending on these values of n we can get different sampling distributions. Now he intends to find the mean of these deviation which he says that is the variance of the sample mean. He says that the variance of the sample distribution will be the ratio of the variance of the original distribution and the number of samples. Now using these values he goes on and explains about the standard error of the mean and other similar concepts. This video gives a good introduction to the concepts of mean, variance and also standard error of the mean.