Question: what is the formula for quartile deviation?
Answer: (IQR = Q3-Q1) Quartile deviation or Semi-interquartile range is one-half the difference between the first and the third quartiles. (QD = Q3-Q1/2) Getting the Quartile Deviation from Ungrouped Data In getting the quartile deviation from ungrouped data, the following steps are used in getting the quartiles: 2. 1.