Statistics is a type of mathematical analysis involving quantified representations, models, and summaries for a given set of empirical data.
General or entire population is a collection of all objects which can be characterized by considered random variable x (or which can be used to study the distribution law of considered random variable x). The general population can be studied by observation only a part of it.
The sample is a part of the general population selected for statistical analysis. The sample should have the following properties.
- The sample must be “fair” and representative to reflect the entire population of interest.
- The sample should contain a “reasonable” number of items being tested or counted.
- The sample is said to be representative if it reproduces the general population well.