Given a sample, the value of the computed sample statistic gives a point estimate of the corresponding population parameter. For example, the sample mean $$(\bar x)$$, is a point estimate of the corresponding population mean, $$\mu$$, or the sample standard deviation $$s$$ is a point estimate for the population standard deviation $$\sigma$$. However, one should note that any randomly selected sample from a population is expected to yield a different value of the sample statistic (sampling error). In other words the sample mean $$\bar x$$ and the sample standard deviation $$s$$ will vary from sample to sample, whereas the population mean $$\mu$$ and the population standard deviation $$\sigma$$ are fixed. Consequently, the point estimate almost always differs from the true value of the population. Therefore, any point estimate should be accompanied with information that indicates the accuracy of that estimate.