where n is the number of integers in your dataset and the result is the position of the number in the sequence dataset so 
here we have the q1 fifth value of 68 the q2 tenth and the median value of 75 and the q3 fifteenth value of 84 the results differ slightly from the spreadsheet results because the spreadsheet calculates them differently your graph would then look like this quartiles are also used to calculate the interquartile range which is a measure of variability around the median the interquartile range is simply the range between the first and third quartiles in this example you d have an interquartile range of 68 to 84 the fifth value to the tenth value in the dataset special considerationsif the data point for q1 is farther away from the median than q3 is from the median then you can say there is a greater dispersion among the smaller values of the dataset than among the larger values the same logic applies if q3 is farther away from q2 than q1 is from the median this is called quartile skewness another aspect to consider is if there is an even number of data points in that case you d use the average of the middle two numbers to get the median in the example above if you had 20 students instead of 19 the median of their scores would be the arithmetic average of the tenth and eleventh numbers 