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Are There Any Outliers?. Using the 1.5*IQR Rule. Say we have the following data: 1,2,5,5,7,8,10,11,11,12,15,20. Notice that you must have ordered data before you can find the Five – Number – Summaries . . Find the median first. It’s the middle point.
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Are There Any Outliers? Using the 1.5*IQR Rule
Say we have the following data:1,2,5,5,7,8,10,11,11,12,15,20 • Notice that you must have ordered data before you can find the Five – Number – Summaries. • Find the median first. It’s the middle point. • Then find the quartiles, Q1 and Q3. They are the middles of the lower and upper half, respectively. • The last thing to do is determine whether there are outliers using the 1.5*IQR Rule
min Q1 Q3 max 1,2,5,5,7,8,10,11,12,12,18,25 1 5 9 12 18 25 -5.5 22.5 1.5IQR IQR = 12 – 5 = 7 1.5IQR 5 - 1.5 * 7 = -5.5 12 + 1.5 * 7 = 22.5 25 is considered an outlier and will be a point in a boxplot and the ‘whisker’ ends at the last non-outlier data point.