The middle 50% of values of the data set is the interquartile range (IQR).
The IQR is given by the formula:
where Q1 is the 25th percent of values and Q3 is the 75th percent of values.
We can get the Q1 and Q3 values as shown below:
Therefore, the Q1 value will be:
and the Q3 value will be:
Therefore, the middle 50% of the scores are given from 66 to 72.
OPTION B is the correct option.