Algebra II : Box and Whisker Plots

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #1 : Basic Statistics

Draw a Box and Whisker plot for the following data set.

\displaystyle 2, 8, 10, 14, 18, 19, 39

Possible Answers:

1c

1b

1a

1d

Correct answer:

1a

Explanation:

Put the data in numerical order (from smallest to largest) if it isn't already. In order to find the median, divide the data into two halves. In order to divide the values into quartiles, find the median of the two halves. 

 

\displaystyle 2, 8, 10, 14, 18, 19, 39

1st quartile: \displaystyle 2\displaystyle 8\displaystyle 10

Median of 1st quartile: \displaystyle 8

 

2nd quartile = Median of total set: \displaystyle 14

 

3rd quartile: \displaystyle 18\displaystyle 19\displaystyle 39

Median of 3rd quartile: \displaystyle 19

 

To construct the Box and Whisker Plot we use the minimum and the maximum value in the data set as the ends of the whiskers. To construct the box, we plot a line at the median of the 1st quartile, the median of our total data set, and at the median of the 3rd quartile. Then we connect the tops and bottom of the lines. The result is as follows: 

1a

The endpoints (black dots) represent the smallest and largest values, in this case, 2 and 39.

Example Question #1 : Box And Whisker Plots

Draw a Box and Whisker plot for the following data set.

\displaystyle 6, 11, 17, 19, 22, 25, 30, 31, 49

Possible Answers:

2c

2d

2a

2b

Correct answer:

2a

Explanation:

Put the data in numerical order (from smallest to largest) if it isn't already. In order to find the median, divide the data into two halves. In order to divide the values into quartiles, find the median of the two halves. 

1st quartile: \displaystyle 6, 11, 17, 19

Median of 1st quartile: \displaystyle \frac{11+17}{2}=\frac{28}{2}=14

2nd quartile = Median: \displaystyle 22 

3rd quartile:\displaystyle 25, 30, 31, 49

Median of 3rd quartile: \displaystyle \frac{30+31}{2}=\frac{61}{2}=30.5 

To construct the Box and Whisker Plot we use the minimum and the maximum value in the data set as the ends of the whiskers. To construct the box, we plot a line at the median of the 1st quartile, the median of our total data set, and at the median of the 3rd quartile. Then we connect the tops and bottom of the lines. The result is as follows: 

2a

Example Question #2 : Box And Whisker Plots

Draw a box and whisker plot for the following data set.

\displaystyle 10, 40, 47, 52, 57, 61, 101

Possible Answers:

3b

3a

3c

3d

Correct answer:

3a

Explanation:

Put the data in numerical order (from smallest to largest) if it isn't already. In order to find the median, divide the data into two halves. In order to divide the values into quartiles, find the median of the two halves. 

1st quartile: \displaystyle 10, 40, 47

Median of 1st quartile: \displaystyle 40

 

2nd quartile = Median: \displaystyle 52

 

3rd quartile: \displaystyle 57, 61,101

Median of 3rd quartile: \displaystyle 61

To construct the Box and Whisker Plot we use the minimum and the maximum value in the data set as the ends of the whiskers. To construct the box, we plot a line at the median of the 1st quartile, the median of our total data set, and at the median of the 3rd quartile. Then we connect the tops and bottom of the lines. The result is as follows: 

 3a

Example Question #3 : Box And Whisker Plots

Draw a Box and Whisker plot for the following data set. 

\displaystyle 17, 32, 47, 51, 53, 55, 57

Possible Answers:

4c

4d

4b

4a

Correct answer:

4a

Explanation:

Put the data in numerical order (from smallest to largest) if it isn't already. In order to find the median, divide the data into two halves. In order to divide the values into quartiles, find the median of the two halves. 

 

1st quartile: \displaystyle 17, 32, 47

Median of 1st quartile: \displaystyle 32

 

2nd quartile= Median: \displaystyle 51

 

3rd quartile: \displaystyle 53, 55, 57

Median of 3rd quartile: \displaystyle 55

 

To construct the Box and Whisker Plot we use the minimum and the maximum value in the data set as the ends of the whiskers. To construct the box, we plot a line at the median of the 1st quartile, the median of our total data set, and at the median of the 3rd quartile. Then we connect the tops and bottom of the lines.

Example Question #3 : Box And Whisker Plots

Draw a Box and Whisker plot for the following data set.

\displaystyle 11, 19, 57, 68, 73, 84, 99, 102, 103

Possible Answers:

5c

5b

5a

5d

Correct answer:

5a

Explanation:

Put the data in numerical order (from smallest to largest) if it isn't already. In order to find the median, divide the data into two halves. In order to divide the values into quartiles, find the median of the two halves. 

1st quartile: \displaystyle 11, 19, 57, 68

Median of 1st quartile: \displaystyle \frac{19+57}{2}=\frac{76}{2}=38

 

2nd quartile = Median: \displaystyle 73

 

3rd quartile: \displaystyle 84, 99, 102, 103

Median of 3rd quartile: \displaystyle \frac{99+102}{2}=\frac{201}{2}=100.5 

To construct the Box and Whisker Plot we use the minimum and the maximum value in the data set as the ends of the whiskers. To construct the box, we plot a line at the median of the 1st quartile, the median of our total data set, and at the median of the 3rd quartile. Then we connect the tops and bottom of the lines. The result is as follows: 

Example Question #4 : Box And Whisker Plots

Draw a Box and Whisker plot for the following data set. 

\displaystyle 3, 9, 12, 21, 30, 39, 60

Possible Answers:

6b

6d

6a

6c

Correct answer:

6a

Explanation:

Put the data in numerical order (from smallest to largest) if it isn't already. In order to find the median, divide the data into two halves. In order to divide the values into quartiles, find the median of the two halves. 

1st quartile: \displaystyle 3, 9, 12

Median of 1st quartile: \displaystyle 9

 

2nd quartile = Median: \displaystyle 21

 

3rd quartile: \displaystyle 30, 39, 60

Median of 3rd quartile: \displaystyle 39 

To construct the Box and Whisker Plot we use the minimum and the maximum value in the data set as the ends of the whiskers. To construct the box, we plot a line at the median of the 1st quartile, the median of our total data set, and at the median of the 3rd quartile. Then we connect the tops and bottom of the lines. The result is as follows: 

Example Question #4 : Box And Whisker Plots

The box and whisker plot above can be used to find all of the following information about the data set that it describes except:

Possible Answers:

The 4 quartiles of the data set

Median Value

Range

The box and whisker plot gives you all of these.

Maximum and minimum values

Correct answer:

The box and whisker plot gives you all of these.

Explanation:

The median value of the data set, 86, is represented by the dashed line inside the box.

The maximum and minimum of the data set, 100 and 75 (respectively), are found at the far ends of the 2 whiskers on either end.

The range of the data set is found by subtracting the minimum from the maximum; 100-75=25, so the range is 25.

The upper and lower quartiles are given by the two boundaries between the box and the whiskers: the lower quartile (1st quartile) is the left boundary, 80 in the data set; the upper quartile (3rd quartile) is the right boundary, which is 92 in the data set.

All of the other choices are provided by the box and whisker plot, so the correct choice is "The box and whisker plot gives you all of these"

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