The arithmetic mean is a mathematical representation of the typical value of a series of numbers, computed as the sum of all the numbers in the series divided by the count of all numbers in the series. The mode of a set of data values is the value that appears most often. The standard deviation is measure of the dispersion and is defined as the root mean square of the deviations. The binomial distribution was first studied in connection with games of pure chance, and it is widely used to analyse data in virtually every field of engineering. The Poisson distribution has become to be recognised as a vitally important distribution in its own right. A Pareto chart, named after Vilfredo Pareto, is a type of chart that contains both bars and a line graph, where individual values are represented in descending order by bars, and the cumulative total is represented by the line.