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Box Plots and Outliers

Box Plots and Outliers. Box Plot. We need 5 numbers, called the 5 number summary: 1. minimum value 2. Q1 3. median 4. Q3 5. maximum value. Harry Potter Data. The 5 number summary is: Minimum 70.9 Q1 78.9 Median 81.35

michael-beard
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Box Plots and Outliers

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  1. Box Plots and Outliers

  2. Box Plot We need 5 numbers, called the 5 number summary: 1. minimum value 2. Q1 3. median 4. Q3 5. maximum value

  3. Harry Potter Data The 5 number summary is: Minimum 70.9 Q1 78.9 Median 81.35 Q3 84.45 Maximum 86.2

  4. Drawing the plot free hand • Use a scaled line to draw the box plot • Approximate locations of the values. • We say this is SKEWED LEFT since the longer tail is on the left side.

  5. Using the TI • Put the data into the list • Press y = ; make sure that there is nothing in the 10 equations

  6. Press 2nd key, y = • There are 3 statistical plots. • Press #1

  7. Turn the plot ON • Select the 2nd box plot • Make the x list L1

  8. Press Zoom • Press Enter on #9

  9. The Box plot will appear

  10. Press TRACE to see values; use right or left arrow keys to move around.

  11. Inter-quartile Range • The inter-quartile range (IQR) is the value of Q3 – Q1

  12. Outliers • An outlier is an unusual score, relative to the data set. It will influence the mean and the standard deviation. • A data set might have no outliers, one outlier, or several outliers. • Two types: Mild and Extreme

  13. Mild Outliers Look for data values (x) that are either: 1. 2.

  14. Extreme Outliers Look for values that are either: 1. 2.

  15. Harry Potter data - checking

  16. Example: Ages of actresses at the time they first won the Oscar

  17. 5 number summary for actresses • Min = 21 • Q1 = 30 • Med = 34 • Q3 = 41 • Max = 80

  18. Actresses • Check for outliers. Identify type.

  19. Box plot with outliers • When we select the 1st box plot on the TI, it allows us to see outliers. Select the mark that is visible for you.

  20. Zoom #9 results in:

  21. Trace and go to the right twice. • The 50 is the last data value that is not an outlier.

  22. Comparison of Boxplots and histograms

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