Mean is a measure of central tendency for data at the interval or ratio level of measurement, commonly called an average. Mean is determined by summing the values or scores in a distribution and dividing by the number of values or scores. Median is a measure of central tendency for data at the interval or ratio levels of measurement. The word mean, which is a homonym for multiple other words in the English language, is similarly ambiguous even in the area of mathematics. In probability and statistics, the population mean, or expected value, is a measure of the central tendency either of a probability distribution or of the random variable characterized by that distribution. - Feller, William (1950).

Mean is simple or arithmetic average of a range of values or quantities, computed by dividing the total of all values by the number of values. The mean of 1, 2, 3, 4, and 5 is (15 รท 5) = 3. It is the most common and best general purpose measure of the mid-point of a set of values, but is prone to distortion by the presence of extreme values and may require use of a measure of distortion, such as, mean deviation or standard deviation.

The population mean, or expected value, is a measure of the central tendency either of a probability distribution or of the random variable characterized by that distribution. The median is one of several indices of central tendency that statisticians use to indicate the point on the scale of measures where the population is centered. The median of a population is the point that divides the distribution of scores in half. Numerically, half of the scores in a population will have values that are equal to or larger than the median and half will have values that are equal to or smaller than the median.

The Mode is one of several measures of central tendency that statisticians use to indicate the point, or points on the scale of measures where the population is centered. It is the score in the population that occurs most frequently. Please notice that the mode is not the frequency of the most numerous score. It is the value of that score itself.