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 Q
Maximum

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 Oscar50 44 35 80 26 28 41 21 61 38 49 33 74 30 31 42 37 34 60 24 27 39 25

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