The article discusses how sample means can be used to estimate population means, even though they are not exactly the same. When samples are taken randomly, the sample mean gives a good estimate of the population mean. The error in estimating the mean decreases as the sample size increases. This error is influenced by the standard deviation of the population. The standard error of the mean shows how reliable an estimate of the population mean is based on a sample mean. It is calculated by dividing the population standard deviation by the square root of the sample size.