ABSTRACT
We have seen three statistical expressions for central tendency: mean, median, and mode. Mean is the arithmetic average of all observations. Each data point contributes to the mean. Median is the middle value of the data array when data are arranged in an order-either increasing order or decreasing order. It is the value of a middle position of the ordered array and does not enjoy contribution from all observations as the mean does. Mode is the most often repeated value. The three are equal for symmetrical distributions such as the normal distribution. In fact, equality of the three values can be used to test if the data are skewed or not. Skew is proportional to the difference between mean and mode.
