ABSTRACT
When estimators talk about a 'Mean Value', they really should say what they mean by the 'Mean', because in statistics there are numerous 'Means' within the general heading of 'Power Means'. Four of these Power Means are of particular importance to estimators: Arithmetic Mean, Geometric Mean, Harmonic Mean, and Quadratic Mean. The Arithmetic Mean or Average of a set of numerical data values is a statistic calculated by summating the values of the individual terms and dividing by the number of terms in the set. The Mode of a set of data is that value which has occurred most frequently, or that which has the greatest probability of occurring. The Mode is often used in defining the specific shape of some standard statistical distributions. The Median of a set of data is that value which occurs in the middle of the sequence when its values have been arranged in ascending or descending order.
