Algebra 1 Common Core Student Edition, Grade 8-9

Think
Why is the
interquartile range
useful?
It represents the middle
of the data set, so it
is not affected by the
minimum, maximum, or
any outliers.

Pr o b l em 2 Making a Box-and-Whisker Plot

Agricult ure The table at the right shows the

amount of crops harvested in the United States

for a certain period. What box-and-whisker

plot represents the data?

Cr o p s H ar v e st e d

Know

A set of data

|N eec^^^_„

A box-and-whisker plot

314

321

315

316

314 10

311

Pl an..

Find the minimum, maximum, and quartiles of the data.

Use these numbers to make the box-and-whisker plot.

Sour ce: U.S. D e p a rtm e n t o f A g ric u ltu re

St e p 1 Order the data to find the minimum, maximum, and quartiles.

303 307 311 312 314 314 314 315 316 316 321

ft f t t

minimum Qt median (Q2) $3 maximum

St e p 2 Draw the box-and-whisker plot.

Cr o p s H ar v e st e d ( m i l l i o n s o f acr es)

Pl o t t h e m i n i m u m ,

quartiles, and

maximum below

a n u m b er l i ne.

307

316

312

314

303

300 305 31

---------

3

i i

315

> <

320 325

• -------------«

Draw a box f rom Q, t o Q3. Draw a

vertical line t hrough the median.

Draw line segment s f rom t he box

to the minimum and maximum.

& G o t It? 2. What box-and-whisker plot represents the following monthly sales, in

millions of dollars, of audio devices: 15 4 9 16 10 16 8 14 25 34?

Pr o b l em 3 Interp reting Bo x -an d -W h isk er Plots

Weather Use the box-and-whisker plots below. What do the interquartile ranges tell

you about the average monthly rainfall for each city?

H 1 h

Average Monthly Rainfall (in.)

—f— l— l— l— l— I— I— l— f - H 1 h

New Orleans, LA •-----------------

Sour ce: National Climatic Data Center

The box for Miami is longer, so Miami has the greater interquartile range.

This greater range means the middle 50% of Miami’s monthly rainfalls vary more widely

than those of New Orleans.

748 Ch ap t er 12 Dat a A n al ysi s an d Pr o b ab i li t y