Section 4-8

Box and Whisker Plots

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A Box and Whisker plot can be used to graphically represent a set of data points

Box whiskers

Parts of a Box and Whisker plot

The range of a set of data is the difference between the greatest and the least values in the data set

Least 15 Greatest 63

Range: 63 – 15 =

Quartiles are the values in a set that separate the data into four sections, each containing 25% or one quarter of the data

Lower quartile Q1

is the median of the lower half of the data

Upper quartile Q3

is the median of the upper half of the data

The median quartile Q2

Separates the dataInto two halves

1.) Given the data points 5, 2, 16, 9, 13, 7, and 10plot the data as a box and whisker plot

Arrange data from least to greatest

2, 5, 7, 9, 10, 13, 16

Now find the median

1.) continued

2, 5, 7, 9, 10, 13, and 16

Now find the least and greatest data points

Now find the midpoint of the lower half

2, 5, 7, 9, 10, 13, and 16

And the midpoint of the upper half

1.) continued

Now plot the points above the number line

1.) continued

Now draw a box to designate the interquartile range from Q1 to Q3 mark the median by drawing a segment through the point in the box

1.) continued

Now add segments (whiskers) connecting the lower quartile to the least value and the upper quartile to the greatest value

Def: An outlier is any data point in a set of data that is extreme15, 21, 34, 35, 37, 39, 42, 44, 50, 112

outlier

Which of these points is not like the others, Which of these points doesn’t belong?

Homework

Page 240Problems: 7, 9 - 15 all