To determine the mode, you might again order the scores as shown above, and then count each one. The most frequently occurring value is the mode. In our example, the value 15 occurs three times and is the model. In some distributions there is more than one modal value. For instance, in a bimodal distribution there are two values that occur most frequently.
Dispersion refers to the spread of the values around the central tendency.
There are two common measures of dispersion, the range and the standard deviation. The range is simply the highest value minus the lowest value. The Standard Deviation shows the relation that set of scores has to the mean of the sample. We know from above that the mean is 20.875. Here, the sum is 350.875.