It isn't easy to measure a parameter such as the mean height or the mean weight of a population. So, we draw samples from the population and calculate the mean height or mean weight of the individuals in the sample. This sample data acts as a representative measure of the population parameter. These sample statistics are known as estimates.

The estimate for the mean of a sample is denoted by ͞x, whereas the mean of the population is designated as μ. Further, parameters such as the mean, proportion, and variance of samples are measured using standard scores, commonly called z scores. Estimates are essential for hypothesis testing, and methods of estimation are used when designing experiments and conducting meta-analyses.