Define Percentiles and Quartiles
Percentiles describe a score’s position within a distribution by dividing the data into 100 equal portions. The location of a score on one of these portions represents its position relative to all other scores;
Quartiles divide a distribution into four equal parts, or quarters. Three quartiles exist for any data set Q1, Q2 , and Q3 corresponding to the 25th, 50th, and 75th percentile respectively. The median is the score at the 50th percentile. Distance between the first and the third quartiles is called the interquartile range.