Answer:
1. In mathematics and statistics, the arithmetic mean, or simply the mean or the average, is the sum of a collection of numbers divided by the count of numbers in the collection. The collection is often a set of results of an experiment or an observational study, or frequently a set of results from a survey.
2. In statistics and probability theory, a median is a value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value.
3. The mode is the value that appears most often in a set of data values. If X is a discrete random variable, the model is the value x at which the probability mass function takes its maximum value. In other words, it is the value that is most likely to be sampled.
4. the set of values that a given function can take as its argument varies.
