Multiple choice general knowledge The inter-quartile range is defined to be Q1 - Q3 Q3 - Q1 (Q1 - Q3)/2 (Q3 - Q1)/2 Reveal answer Fill a bubble to check yourself B Correct answer Explanation The inter-quartile range (IQR) measures the spread of the middle 50% of data. It is calculated as Q3 (75th percentile) minus Q1 (25th percentile), representing the range between the upper and lower quartiles.