In statistics, which quantity is denoted by σ2?

The quantity denoted by σ² represents the population variance. Population variance is a measure of how much the data points in a population deviate from the population mean. It is calculated as the average of the squared differences from the mean, providing insight into the dispersion of the entire dataset.

The notation σ² specifically indicates that it is derived from the entire population rather than just a sample, which is why it is important to distinguish it from the sample variance, represented by s². Population variance is used when considering the entire set of data points, while sample variance serves the purpose of estimating variance based on a subset of the population. Understanding this distinction is crucial in statistical analyses, as it affects the interpretation and application of results based on the type of data you are working with.

This understanding reinforces the importance of knowing whether you are dealing with data from the entire population or a sample, as it has implications for further statistical calculations and the validity of inferences drawn from the data.