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3. 2 Interquartile Range. Interquartile Range = Upper Quartile – Lower Quartile. 23471222465835681014 Median = 29 L.Q. = 14 U.Q. = 47 Interquartile Range = 47 – 14 = 33 10 12 14 22 23 35 46 47 58 68 70 Median = 35 L.Q. = 14 U.Q. = 58 Interquartile Range = 58 – 14 = 44 What if there is an extra number ? Menu

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5. 4 Why do we bother with the Interquartile Range ? Why don’t we simply use the Range all of the time ? Sarah’s exam marks : 88 %, 90 %, 89%, 91%, 92%, 93%, 89%, 90% Range = 93 – 88 = 5% (Small Range) A Small Range means that Sarah is very consistent, predictable, reliable. Mark’s exam marks : Range = 94 – 32 = 62% (Big Range) A Big Range means that Mark is very inconsistent, unpredictable, unreliable. But Mark is predictable ! It was only the 32% that gave the impression that he is inconsistent ! I will try the Interquartile Range ! 32% 88%89% 90% 91%92% 94% Median = 90.5 L.Q. = 88.5U.Q. = 92 Interquartile Range = 92 – 88.5 = 3.5 (Small Interquartile Range) This small Interquartile Range shows that Mark is consistent. A small Interquartile Range also shows that the Middle half of the numbers are bunched together. Menu