12-4 Box-and-Whisker Plot
Getting Ready…
Suppose you are moving to a new town and are looking for a warm climate. You can choose
between Morrel or Glenville. Based on the average monthly temperatures below, which town
would you choose? How did you decide?
Month
Jan
Morrel
56
Glenville 58
Feb
57
52
Mar
60
66
Apr
68
70
May
74
76
Jun
82
78
Jul
83
81
Aug
85
84
Sep
79
77
Oct
70
73
Nov
62
68
Dec
55
63
What Is a Box-and-Whisker Plot?
● A box-and-whisker plot is a way to display data. The box-and-whisker plots shows the
________, __________________________, and ________________________.
● The left whisker and right whisker each contain ___ of data.
● The box (______________________) contains about ___ of data.
Key Terms
●
●
●
●
●
●
Lower Quartile: The ________ of the lower half of the number
Upper Quartile: The ________ of the upper half of the number
Lower Extreme: _______ number in the data set
Upper Extreme: _______ number in the data set
Quartiles: Values that divide a data set into four ______ parts
Interquartile Range: The difference between the ______ and ______ quartiles
True or False or Undetermined?
(________)25% of the sophomores spend between 48 & 60 minutes per night on homework.
(________) In general, these sophomores spend more time watching TV than doing
homework.
(________) The TV box & whisker graph contains more data than the homework graph.
(________) Some sophomores didn't watch TV that month.
(________) 15% of the sophomores didn't watch TV that month.
(________) The TV data is more varied than the homework data.
Example 1: Shawn’s Income
Shawn has earned an amount of income each month for the past 8 months (In dollars)
125, 80, 140, 135, 126, 140, 350, 75
Lower
Quartile
Upper
Quartile
Lower
Extreme
Upper
Extreme
Interquartile
Range
Median
Problem 1: US Agriculture
You are a staff in the US Department of Agriculture, and your job is to make a box-and-whisker
plot on the number of crops harvested in USA from 2012 to 2022 (See table below)
Problem 2
The box-and-whisker plots below show the normal precipitation (in inches) each month in Dallas
and in Houston, Texas.
a. For how many months is Houston’s precipitation less than 3.5 inches?
b. Compare the precipitation in Dallas with the precipitation in Houston. (tips: consider
median, interquartile range, and range)
Problem 3
Use the box-and-whisker plots below. What do the interquartile ranges tell you about the average
monthly rainfall for each city?
Problem 4
Of 25 test scores, eight are less than or equal to 75. What is the percentile rank of a test score of
75? (
)
A. 8 B. 17 C. 32 D. 75
Drawing a Box and Whisker Plot
1.
2.
3.
4.
5.
6.
7.
Collect and organize your data. ...
Calculate the median. ...
Calculate each of the quartiles. ...
Create your plot line and draw a line for each of your quartiles. ...
Create a box connecting the quartiles. ...
Find the interquartile range. ...
Find the new upper and lower limits…
Benefits of a Box and Whisker Plot
take up less space
give information as a whole
compare data much quicker
Answers
1. True 2. True 3. Cannot be Determined 4. True 5. Cannot be Determined 6. True
Problem 1:
In a box-and-whiskers plot, we need to find the minimum, maximum, and three quartiles before
we graph the plot: 303(Minimum), 307, 311(Q1), 312, 314, 314(Q2), 314, 315, 316(Q3) , 316,
321(Maximum)
Problem 3:
The box for Miami is longer than the box of New Orleans, thus greater interquartile range.
The range for Miami is larger, thus rainfalls vary more widely.