What is a sample?

A sample is fundamentally defined as a part of a population that is used for analysis. In statistics, researchers often use samples because it’s usually impractical or impossible to collect data from every individual in a population. By selecting a smaller, representative subset, analysts can make inferences about the entire population while minimizing costs and time involved in data collection. This is crucial in fields where obtaining data from the entire population isn't feasible.

The other options relate to statistical concepts but do not accurately describe what a sample is. A method of variance calculation refers to how variation within data is quantified, while the total number of observations describes the size of the dataset, and the median represents the middle value in a data set. None of these options correctly encapsulate the idea of a sample as a subset of a larger group used for analysis purposes.