Studying the central tendency alone is not sufficient because apart from calculating the value of the central point of a group of data ( which is what the measure of central tendency does), it is important to also understand the spread of these data about the average(mean) value.The measure of dispersion will help us to know the range of error that is recorded in both descriptive and inferential statistics and this will enable the statistician to assess the validity of the data generated from the experiment performed.
A small value of standard deviation indicates that each of the values in the dataset is close to the average (mean) value.
