In statistics, a parameter is any measured quantity of a statistical population that summarizes or describes an aspect of the population, such as a mean or a standard deviation. Parameters are numbers that describe the properties of entire populations, and they are used to define a given population. They are used to describe a specific characteristic of the entire population, and they are fixed numerical values for populations. The most commonly used parameters are the measures of central tendency, such as mean, median, and mode, and they are used to describe how data behaves in a distribution.
On the other hand, a statistic is a number describing a sample, which is a subset of the population. A statistic is an estimated measurement of the parameter based on a subsample. When making an inference about the population, the parameter is unknown because it would be impossible to collect information from every member of the population. Rather, we use a statistic of a sample picked from the population to derive a conclusion about the parameter.
To differentiate between a parameter and a statistic, it is important to ask whether the number describes a whole population or a small part of the population. The word "parameter" rarely pops up in statistics because all we deal with is statistics. However, when we see something like "population mean," it makes it more obvious that its about the whole parameter.
