In probability theory and statistics, a<unk>  is described as the number separating the higher half of a sample, a population, or a probability distribution, from the lower half. The<unk>  of a finite list of numbers can be found by arranging all the observations from lowest value to highest value and picking the middle one. If there is an even number of observations, the<unk>  is not unique, so one often takes the mean of the two middle values.
At most half the population have values less than the<unk>  and at most half have values greater than the<unk> . If both groups contain less than half the population, then some of the population is exactly equal to the<unk> .
Median
Average
Arithmetic mean
Absolute deviation
Trends 
Incidence 
Dose Profile
Prevalence