35,23,32,25,27,31,29,30 1st: Order data from smaller to greater: 23,25,27,29,30,31,32,35
2nd Find the median of the set (central value). Since the number of data is even, then the median is the average between 29 & 30 = (29+30)/2 =29.5,(we will not use the median value, just for indication)
3rd, Find the central value of the subset on the left of 29 (that is 23,25,27) This lower median =25 . This is called Q1 4th , Do the same with the subset on the right of 30 (that is 31,32,35). This higher median = 32 is called Q3 (for your info the 1st median=29.5 is Q2) The IQR or inter quartile range is Q3 - Q1 (or upper - lower Q) IQR = 32-25) =7