7th Grade Math

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Measures of Variation

PART A B

Multi-Part

Lesson 2

SPI 0706.5.1

Interpret and employ various

graphs and charts to

represent data. SPI 0706.5.3

Calculate and interpret the

mean, median, upper-

quartile, lower-quartile, and

interquartile range of a set

of data. Also addresses

GLE 0706.5.1, GLE 0706.5.2,

GLE 0706.5.4.

504 Statistical Displays

Main Idea

Display and interpret

data in box-and-whisker

plots.

Vocabulary

box-and-whisker plot

Box-and-Whisker Plots

FOOTBALL The line plot shows the

number of touchdowns scored by each of the

16 teams in the National Football Conference

in a recent year.

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× ××× ××××× ××

×

×

×

× ×

1. Find the median, quartiles, and range of the data.


2. What percent of the teams scored less than 30 touchdowns?


3. What percent of the teams scored more than 37 touchdowns?

The medians and quartiles divide the data into four equal parts. The

line plot shows that there are four pieces of data in each part.

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× ××× ××××× ××

×

×

×

× ×

LQ median UQ

A box-and-whisker plot is a diagram that is constructed using the

median, quartiles, and extreme values. A box is drawn around the

quartile values, and the whiskers extend from each quartile to the

extreme values. The median is marked with a vertical line. The figure

below is a box-and-whisker plot of the football data.

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lower extreme LQ median UQ upper extreme

You can see all the pieces of data in a line plot, but in the box-and-

whisker plot you can see only the median, quartiles, and extreme

values. Box-and-whisker plots separate data into four parts. Even

though the parts may differ in length, each contains 25% of the data.

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25% of

the data

25% of

the data

25% of

the data

25% of

the data

V

b

498_509_C09_L2_895130.indd 504 1/11/10 9:34 AM