1. Lesson 13.8 Interpret Box-and-Whisker Plots
Essential Question: How do you make and interpret box-and-whisker plots?

2. Arrange the following numbers in numerical order
Before we start…
Arrange the following numbers in numerical order
What is the median?
What is the minimum value?
What is the maximum value?

3. What is a box-and-whisker plot?
It organizes data values into four groups.
lower and upper halves
lower quartile = median of lower half
upper quartile = median of upper half

4. How do you make a box-and-whisker plot?
Order the data.
Find the median and the quartiles.
Plot the median, the quartiles, the maximum value, and the minimum value below a number line.
Draw a box from the quartiles and then connect the maximum and minimum values with “whiskers”.

5. Song Lengths The lengths of songs (in seconds) on a CD are listed below. Make a box-and-whisker plot of the song lengths.
173, 206, 179, 257, 198, 251, 239, 246, 295, 181, 261

6. Televisions The prices (in dollars) of 27-inch television sets at an electronics store are given below. Make a box-and-whisker plot of the television prices.
188, 225, 192, 239, 271, 286, 224, 334, 316, 275

7. How do you interpret box-and-whisker plots?
4 parts:
2 parts of the box
25% of data
2 parts of whiskers
Each part contains approximately the same number of data values

8. What is the interquartile range?
Is the difference of the upper quartile and the lower quartile

10. The box-and-whisker plots below show the normal monthly wind speeds (in miles per hour) in Athens and Savannah, Georgia.
For how many months is Athens’ wind speed more than 8.3 miles per hour?
Compare the wind speeds in the two cities.

11. What is an outlier?
A value that is widely separated from the rest of the data
Is the value 1.5 times greater or less than the quartile value?

12. The normal monthly amounts of precipitation (in inches) in Dallas are: 1.9, 2.4, 3.1, 3.2, 5.2, 3.2, 2.1, 2.0, 2.4, 4.1, 2.6, 2.6. Which value, if any, is an outlier?

13. Which value, if any, is an outlier in the data set?
3.7, 3.0, 3.4, 3.6, 5.2, 5.4, 3.2, 3.8, 4.3, 4.5, 4.2, 3.7

14. How do you make and interpret box-and-whisker plots?

15. Ticket Out the Door