Multiple choice general knowledge Quartile Deviation is (Q3 - Q1)/2 (Q3 + Q1)/2 (Q3 - Q1)/4 (Q3 + Q1)/4 Reveal answer Fill a bubble to check yourself A Correct answer Explanation Quartile deviation (QD) is defined as half the inter-quartile range: QD = (Q3 - Q1)/2. It is also called semi-inter-quartile range and measures the average spread from the median.