WALK THRU Interquartile Range IQR The IQR is

WALK THRU Interquartile Range (IQR) The IQR is a measure of statistical dispersion which looks at the middle 50% of your data spread When? To look at the spread of your data through the central 50%. Step 1 Step 2 Step 4 Step 3 Step 5 Step 6 Arrange your data in numerical order. Find the median (middle point). If this is located between 2 set of data e. g. 12 and 14, the median would be 13. Benefits? The IQR is not affected by anomalies and is therefore a better measure of spread than the range. Issues? The first and fourth quarters of your data aren’t used so any anomalies within this data is not taken into account. Find the Upper Quartile (UQ). This is located between the highest data point and the median. To calculate the Interquartile Range use the equation IQR = UQ – LQ. Find the Lower Quartile (LQ). This is located between the lowest data point and the median. To present this visually, a box and whisker plot could be created.

WALK THRU Step 1 The IQR is a measure of statistical dispersion which looks at the middle 50% of your data spread Interquartile Range (IQR) Arrange data in number order 1 4 5 6 8 9 9 9 11 13 Step 2 1 4 5 6 8 9 9 9 11 13 Find the median Step 3 Find the LQ Step 4 Find the UQ Step 5 IQR = UQ - LQ Step 6 Present using a box & whisker plot 14 14 17 17 18 18 19 19 20 20

WALK THRU The IQR is a measure of statistical dispersion which looks at the middle 50% of your data spread Interquartile Range (IQR) Step 1 Arrange data in number order Step 2 Find the median Step 3 Find the LQ 1 4 5 6 8 9 9 9 11 13 14 Step 4 Find the UQ Step 5 IQR = UQ - LQ Step 6 Present using a box & whisker plot 7 UQ (15. 5) – LQ (7) = IQR (8. 5) 15. 5 17 18 19 20

WALK THRU Step 1 Arrange data in number order Step 2 Find the median Step 3 The IQR is a measure of statistical dispersion which looks at the middle 50% of your data spread Interquartile Range (IQR) Student Task Use the following sets of data to find the IQR and draw a box and whisker plot to present the IQR. Average of individual at a shopping centre 31 45 76 34 16 32 24 65 20 56 24 64 36 38 41 16 Find the LQ Step 4 Find the UQ Step 5 IQR = UQ - LQ Step 6 Present using a box & whisker plot Number of minutes spent exercising this week 65 60 60 15 10 30 45 30 30 0 15 60 120 0 90 60