Algebra 1 Common Core Student Edition, Grade 8-9

Bo x- an d - W h isk er Plot s

S- I D. A. 2 Use st at ist ics ap p ro p riat e t o t he... dat a

distribution to compare center... and spread... of two

or more different data sets. Also N-Q.A.1, S-ID.A.1

MP 1, MP 2, M P3, MP 4, MP 6

Co m m o n Co r e St at e St a n d a r d s

Object ives To make and interpret box-and-whisker plots

To find quartiles and percentiles

Get t in g Read y! « X C

What criteria are

you going t o use t o

decid e?

MATHEMATICAL

PRA CTI CES

Su p p o se y o u a r e m o vi n g t o a n e w t o w n an d a r e l o o k i n g f o r a w a r m

clim at e. You can choose between M orrell or Glenville. Based on the

averag e monthly t em p erat ures below, which town would you choose?

How did you d ecid e?

Average Monthly Temperatures

Lesso n

Vocabulary

quartile

interquartile

range

box-and-whisker

plot

percent ile

percentile rank

Month Jan Feb Mar Apr May Jun Jul A u g Se p t Oc t Nov Dec

Morrell 56 57 60 68 74 82 83 85 79 70 62 55

Glenville 58 62 66 70 76 78 81 8 4 77 73 68 63

In the Solve It, you may have looked at different parts of each data set in order to

compare the two data sets.

| Es s e n t i a l U n d e r s t a n d i n g Separating data into subsets is a useful way to

summarize and compare data sets.

Quar t i l es are values that divide a data set into four equal parts. The median (or second

quartile, Q2) separates the data into upper and lower halves. The first quartile (Qj) is

the median of the lower half of the data. The third quartile (Q3) is the median of the

upper half of the data. The interquartile range is the difference between the third and

first quartiles.

11 12 13 21 2 3 2 5

t I I t

minimum Qi median (Q 2 ) Q 3 maximum

[— i n t er q u ar t i l e r an g e = Q 3 - Q 1 - * j

For a set of data that has an odd number of values, you do not include the median in

either half when finding the first and third quartiles.

746 Ch ap t er 12 Data Analysis and Probability