Chapter 1. Graphing Skills Tutorial

Line Graphs

Graphing Skills Tutorial
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Line graphs are used when the independent variable is represented by a numerical sequence (1, 2, 3…) rather than discrete categories (red, yellow, blue…). The dependent variable is always a numerical sequence.

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1.

Cumulative Loss of Glacier Mass Line Graph

This graph illustrates loss of ice from all glaciers since 1945. What is the unit of measure for loss?

A.
B.
C.
D.

Correct. Units are given in the label for each axis; the y-axis on this graph is labeled meters.
Incorrect. Units are given in the label for each axis; the y-axis on this graph is labeled meters.
 

Scatterplots

Scatterplots (with or without a trendline) are used when any x-value could have multiple y-values.

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4.

Exposure to Particulate Matter and Mortality

Based on this graph, what city had the highest mortality rate between 1974-1989, and what was the average amount of small particulates measured in the air in that city during those years?

A.
B.
C.
D.

Correct. The green dots represent the years 1974-1989, and the “S” in the dot stands for Steubenville.

Incorrect. A is incorrect; Harriman did not have 30 ug/m3 of particulate matter in those years. B is incorrect; 22 ug/m3 is Steubenville’s value for the years 1990-1998. D Is incorrect; Portage served as the comparison city, but its levels of particulate matter pollution were never 1 ug/m3.

 

Pie Charts

Pie charts are useful when the groups represented by the independent variable are all discrete categories (e.g., red, yellow, blue…) rather than a numerical sequence (e.g., 1, 2, 3…). In addition, the categories also represent all the subsets of a whole—all the category values add up to 100%.

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6.

U.S. Electricity Generation by Fuel, 2010

How much of total electricity produced in the U.S. comes from renewables such as solar and wind energy?

A.
B.
C.
D.

Correct. This is represented by the green slice of the pie labeled renewables.

Incorrect. A is the amount from coal, B is the amount from natural gas, and D is the amount from petroleum.

 

Bar Graphs

Bar graphs are appropriate when the values for the independent variable represents discrete, separate groups. The independent variable goes on the x-axis and the dependent variable goes on the y-axis.

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8.

Percent of Species Listed As Endangered Compared to the Estimated Size of the Group

What percentage of known fungal species are listed as threatened or endangered? Click the chart above to view a larger version.

A.
B.
C.
D.

Correct. According to this graph, no species of fungus is listed as threatened or endangered.

Incorrect. According to this graph, no species of fungus is listed as threatened or endangered.

 

Area Graphs

Area graphs are used when we want to view the relative proportion of each group and the independent variable is a numerical sequence.

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10.

Catch Tonnage Area Graph

Between the years 1950 – 1992, what was the most abundant seafood type caught on the Newfoundland-Labrador Shelf?

A.
B.
C.
D.

Correct. Even after the initial decline in the early 70’s, cod remained the most caught fish.

Incorrect. A, C, and D are all incorrect. Salmon were abundant between 1970-1990, but they were not captured more than cod. Herring were never a huge fraction of the catch, even though they too were more common prior to 1980. Molluscs have become a more commonly captured species since 1991, but they are still not the most common type of seafood captured.