Quartiles are the values that divide a data set into quarters: Put the values in order Divide the list into four equal parts The Quartiles are at the divisions The interquartile range shows the range ...

There are 30 students, so we are looking for the group which contains the \((30 + 1) \div 2 = 15\frac{1}{2}th\) value, which lies halfway betwen the 15th and the 16th value. The cumulative frequency ...