Quartile

Not the coin. Not the periods of either football or basketball games. Instead a quartile is a divider in a data set. We take the numbers in a data set, numerically order them, and then divide the data set into four equally-sized groups of data points. The three points that are the dividers mark the quartiles.

They’re located at 25% of the data, 50% of the data, and 75% of the data. The quartile at 25% is called Q1, the 25th percentile and the first quartile, and it’s the top end of the data running from the lowest data point to Q1. The quartile at 50% is called Q2, the 50th percentile, and the median (yes, that median...the middle of a data set), and it’s the top end of the data running from Q1 to Q2. The quartile at 75% is called Q3, the 75th percentile, and the third quartile, and it’s the top end of the data running from Q2 to Q3 as well as the lower end of the data running from Q3 to the largest data point..