Histograms and Box and Whisker Plots

Introduction to
Dot Plots, Histograms and Box Plots

Important Terms

• Data: information in number form

• Frequency: How often something happens

• Outliers: a piece of data that has a value much less than or much greater than the rest of the data

• Range: The difference between the minimum value and the maximum value in a data set.

• Minimum: the piece of data that has the least value in a set of data.

• Maximum: the piece of data that has the most value in a data set.

​Dot Plot

​Organizes a set of data on a number line.

Dot Plots

• Displays the frequency (how often) of each data value in a data set.

• Sometimes called a line plot

• The total number of x's or dots equals the total number of data values in the set of data.

Multiple Choice

What day were the least amount of cars sold?

• Monday

• Tuesday

• Thursday

• Saturday

Multiple Choice

The dot plot show the distances, in miles cyclists completed on Saturday. How many cyclists went at least 11 miles?

• 10

• 1

• 3

Histograms

• A histogram is a graphical display of data using bars of different heights.

• In a histogram, each bar groups numbers into intervals or ranges or numbers.

Histograms can tell us:

• Mode

• Frequency

• Intervals

To Construct a Histogram

1. Draw and label the x and y axis.

2. Represent the frequency (how many data points in the interval) on the y-axis and the intervals on the x-axis.

3. Using the frequencies as the heights, draw the vertical bars for each class.

Multiple Choice

The histogram shows the ages of the members of the community chorus. How many people in the chorus are between 20 and 30?

• 4

• 15

• 12

Multiple Choice

Which interval has 4 students?

• 56-59

• 60-63

• 60-67

• 48-51

Multiple Choice

Which histogram matches the data set?

Box Plot

• A box plot—also called a box and whisker plot—displays the five-number summary of a set of data. In a box plot, we draw a box from the first quartile to the third quartile.

Box Plot

​​The five-number summary:

Min: Minimum or lowest number in the data set
Max: Maximum or highest number in the data set
Median: The value in the middle of the data set when the numbers are in order from least to greatest
Lower Quartile: The median of the lower half of the data when the numbers are in order
Upper Quartile: The median of the upper half of the data when the numbers are in order

Multiple Choice

What is the median of the data represented by the box plot?

• 65

• 12.5

• 20

Multiple Choice

The box plot represents this data set. {16, 16, 16, 18, 18, 20, 24, 28, 30, 34} What value does the letter "A" represent on the box plot of the data?

• 20

• 16

• 18