1. 11.2 box and whisker plots

2. What we will learn Make and use box and whisker plots
Interpret box and whisker plots
Use to compare data sets

3. Needed vocab
Box and whisker plot: shows the variability of a data set along a number line using least, greatest, and quartiles.
Quartile: divide data set into four equal parts
Five number summary: least value, first quartile, median, third quartile, and greatest value that make up a box and whisker plot
Interquartile range: represents the middle half of the data

4. Ex. 1 making a box and whisker plot
Steps
1. put numbers in numerical order
2. make a number line
3. put a dot at highest and lowest value
4. find median and put a dot
5. find Q1
Median of low to median
6. find Q3
Median of high to median
Make a box and whisker plot of:
24, 30, 30, 22, 25, 22, 18, 25, 28, 30, 25, 27

5. Your practice
A basketball player scores 14, 16, 20, 5, 22, 30, 16, and 28 points during a tournament. Make a box and whisker plot that represents the data.
5, 14, 16, 16, 20, 22, 28, 30

6. Ex. 2 Interpreting
Interquartile range (IQR) is third quartile (Q3) – first quartile (Q1)
Range of middle half of data

7. Ex. 2 continued
The box and whisker plot represents the lengths (in seconds) of the songs played by a rock band at a concert.
A. find and interpret the range of data
Range is high minus low
To interpret: things vary by this amount
B. describe the distribution of the data
25% in each whisker
50% in the box
C. find and interpret the interquartile range
Q3 - Q1, middle half varies by this amount
D. is the data more spread out below Q1 or above Q3?
Look for longer whisker

8. Ex. 2 Continued A. find and interpret range of the data
300 – 160 = 140, so length of songs vary by 140 seconds
B. describe distribution
25% between 160 and 220 seconds
50% between 220 and 280 seconds
25% between 280 and 300 seconds
C. find and interpret interquartile range
280 – 220 = 60, so middle half of songs vary by 60 seconds
D. where is data more spread out
Below Q1

9. Ex. 3 Comparing Box and Whisker Plots

10. Ex. 3 Continued A. identify the shape of each distribution
Your class – skewed left
Friend’s class - symmetric
B. which scores are more spread out?
Friend’s class