The mean is the average that is obtained when you divide the total of the given quantities with their total number while median is the value that is at the middle of a list values arranged in a specific order. Mode on the other hand is the value that appears more frequently in the given list of values. It is important to know the value of each central tendency as they give a clear description of the whole set of data they enable you to condense vast figures and make it easier for you compare two that are obtained from different battery tests. However the use of percentile ranks as standardized scores may have some disadvantages. The percentiles denote positions hence cannot be easily combined to find averages of different groups of data for example in a school. The percentiles are also usually compressed at the center of score ranges and as a results of this a small change in the standardized score causes a big change in the percentile ranks. The teacher has to therefore take great care when considering the percentile rank changes of the students of the different tests. [...]
ANSWER THE QUESTIONS AND USE THIS BOOK. Sharon Robinson Kurpius and Mary Stafford (2006), Testing and Measurement: A User Friendly Guide, Sage Publication, Thousand Oaks, CA.