Unit 2Section 2.2

2.2: More Graphs and Displays

Several types of graphs are used in statistics besides histograms, frequency polygons, and ogives.

Other graphs include: Stem and Leaf Dot Plots Pie Graphs Pareto Charts Scatter Plots Time-Series Graphs

Stem and Leaf Plot

Stem and Leaf Plot– data plot that uses part of the data values as the stem and part of the data values as the leaf to form groups or classes.

Tips for Drawing Stem and Leaf Plot Arrange the data in order.

The trailing digit becomes the “leaf,” while the first digit(s) becomes the “stem.”

i.e. for the number 14, 1 is the stem and 4 is the leaf. i.e. for the number 115, 11 is the stem and 5 is the leaf.

Data is grouped in order based on values that share the same stem.

Section 2.2

Example 1: Stem and Leaf Plot

Create a Stem and Leaf plot using the following info:

Number of Cardiograms Performed Over 20 Days

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25 31 20 32 13

14 43 02 57 23

36 32 33 32 44

32 52 44 51 45

Dot Plot

Dot Plot – each data entry is plotted using a dot on a number line.

Tips for Drawing Dot Plot Make sure your number line contains the lowest

and highest data value. Pick a scale that is easy to use

Plot each data value above the corresponding number on the number line.

If a value is represented two or more times, plot additional dots above the previous.

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Example 2: Dot Plot Create a Dot plot using the following

info:

Number of Cardiograms Performed Over 20 Days

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25 31 20 32 13

14 43 02 57 23

36 32 33 32 44

32 52 44 51 45

Pie Graph

Pie Graph– a circle that is divided into sections or wedges according to the percentage of frequencies in each category of the distribution.

Tips for Drawing Pie Graphs Determine the degree measure for each piece of the

pie. Take the frequency, divide it by the sum of the frequencies,

then multiply it by 360 degrees. Determine the percentage for each piece of the pie. Create the graph

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Example 3: Pie Graph Create a Pie Graph using the

following info:Pounds of Snacks Eaten During the Super

Bowl

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Snack Pounds (Frequency)

Potato Chips 11.2 million

Tortilla Chips 8.2 million

Pretzels 4.3 million

Popcorn 3.8 million

Peanuts 2.5 million

Pareto Charts

Pareto Chart – used to represent a frequency (or relative frequency) distribution for a categorical variable.

Frequencies are displayed as the height Bars are arranged from the highest to the lowest.

Tips for Drawing Pareto Charts Make the bars the same width. Arrange the data from largest to smallest

according to frequency. Make the units that are used for the frequency are

equal in size.

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Example 4: Pareto Chart Create a Pareto Chart using the

following info:Average Cost Per Mile for Passenger

Vehicles on State Turnpikes

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State Number

Indiana 2.9 cents

Oklahoma 4.3 cents

Florida 6.0 cents

Maine 3.8 cents

Pennsylvania 5.8 cents

Homework Pg. 62 (5 – 11 ODD, 17, 23, 25, 27)

Read and take notes on Section 2.2 (pgs. 60-61)

Section 2.2