Algebra 1 Common Core Student Edition, Grade 8-9

...
How do you find
the first quartile fo r
an even num ber of
values?
The first quartile is the
median of the lower
half of the data, so you
find the mean of the
middle tw o values in the
lower half.

What are the minimum, first quartile, median, third quartile, and maximum of the

data set below?

125 80 140 135 126 140 350 75

Su m m a r i zi n g a D a t a Set

St e p 1

St e p 2

Arrange the data in order from least to greatest.

75 80 125 126 135 140 140 350

Find the minimum, maximum, and median.

75 80 125 126 135 140 140 350

median (Q2) =126 + 135 130.5

St e p 3

The minimum is 75. The maximum is 350. The median is 130.5.

Find the first quartile and the third quartile.

75 80 125 126 135 140 140 350

first quartile (Qx) = 80 + 125 = 102.5

third quartile (Q3) =140 + 140 140

The first quartile is 102.5. The third quartile is 140.

Go t I t? 1. What are the minimum, first quartile, median, third quartile, and maximum

of each data set?

a. 95 85 75 85 65 60 100 105 75 85 75

b. 11 19 7 5 21 53

A box-and-whisker plot is a graph that summarizes a set of data by displaying it along

a number line. It consists of three parts: a box and two whiskers.

H h H h

Bo x- an d - Wh i sk er Pl o t

H 1----- 1 ----- 1 ----- 1 -----1—

whisker

___

box-

o

H 1----- 1

whisker

A___

minimum t

Q 1

f

median (Q2)

i

Qb

maximum

The left whisker extends from the minimum to the first quartile.

It represents about 25% of the data.

The box extends from the first quartile to the third quartile and has a

vertical line through the median. The length of the box represents the

interquartile range. It contains about 50% of the data.

The right whisker extends from the third quartile to the maximum.

It represents about 25% of the data.

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S ........r-----------------———--------—------------------'............................—-...................;— S 3 & S :

NM L I *-e s s o n !2-4 Box-and-Whisker Plots^747

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