# Martin earned the following scores on his last five tests. 98, 78, 84, 75, 91 What is the interquartile range of his scores?

98, 78 , 84, 75, 91 The interquartile range formula is the first quartile subtracted from the third quartile:IQR = Q3 – Q1.**************************************************** Step 1: Put the numbers in order. 75, 78, 84, 91, 98 Step 2: Find the median. 75, 78, 84, 91, 98 Step 3: Place parentheses around the numbers above and below the median. Not necessary statistically, but it makes Q1 and Q3 easier to spot. (75, 78), 84, (91, 98) Step 4: Find Q1 and Q3 Think of Q1 as a median in the lower half of the data and think of Q3 as a median for the upper half of data. (75, 78), 84, (91, 98) *(75, 78) ---> (75 + 78) ÷ 2 = 76.5 *(91, 98) ---> (91 + 98) ÷ 2 = 94.5 Step 5: Subtract Q1 from Q3 to find the interquartile range. 94.5 – 76.5 = 18 IQR = 18