Are There Any Outliers?

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# Are There Any Outliers? - PowerPoint PPT Presentation

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?

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Presentation Transcript

### 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.