# scientific graphing

## line graphs

Consider the data in Table 1.3. It lists the number of tornadoes in the U.S. per month, averaged over the years 2009 to 2011. Month January February March April May June July August September October November December Average Number of Tornadoes 17 33 74 371 279 251 122 57 39 65 39 34 Line graphs are especially useful for showing changes over time, or time trends in data, such as how the average number of tornadoes varies throughout the year. Therefore, a line graph would be a good choice to display the data in the Table 1.3. The line graph below shows one way this could be done. Q: Based on the line graph above, describe the trend in tornado numbers by month throughout the course of a year. A: The number of tornadoes rises rapidly from a low in January to a peak in April. This is followed by a relatively slow decline throughout the rest of the year.

Rank City 1 2 3 4 5 6 7 8 9 10 Clearwater, FL Oklahoma City, OK Tampa-St. Petersburg, FL Houston, TX Tulsa, OK New Orleans, LA Melbourne, FL Indianapolis, IN Fort Worth, TX Lubbock, TX Average Number of Tornadoes(per 1000 Square Miles) 7.4 2.2 2.1 2.1 2.1 2.0 1.9 1.7 1.7 1.6 Bar graphs are especially useful for comparing values for different things, such as the average numbers of tornadoes for different cities. Therefore, a bar graph is a good choice for displaying the data in theTable 1.1. The bar graph below shows one way that these data could be presented. Q: What do the two axes of this bar graph represent? A: The x-axis represents cities, and the y-axis represents average numbers of tornadoes. Q: Could you switch what the axes represent? If so, how would the bar graph look? A: Yes; the x-axis could represent average numbers of tornadoes, and the y-axis could represent cities. The bars of the graph would be horizontal instead of vertical.

## circle graphs

The data in Table 1.2 shows the percent of all U.S. tornadoes by tornado strength for the years 1986 to 1995. In this table, tornadoes are rated on a scale called the F scale. On this scale, F0 tornadoes are the weakest and F5 tornadoes are the strongest. Tornado Scale(F-scale rating) F0 F1 F2 F3 F4 F5 Percent of all U.S. Tornadoes 55.0% 31.6% 10.0% 2.6% 0.7% 0.1% Circle graphs are used to show percents (or fractions) of a whole, such as the percents of F0 to F5 tornadoes out of all tornadoes. Therefore, a circle graph is a good choice for the data in the table. The circle graph below displays these data. Q: What if the Table 1.2 on tornado strength listed the numbers of tornadoes rather than the percents of tornadoes? Could a circle graph be used to display these data? A: No, a circle graph can only be used to show percents (or fractions) of a whole. However, the numbers could be used to calculate percents, which could then be displayed in a circle graph.

## using graphs in science

Graphs are very useful tools in science. They can help you visualize a set of data. With a graph, you can actually see what all the numbers in a data table mean. Three commonly used types of graphs are bar graphs, circle graphs, and line graphs. Each type of graph is suitable for showing a different type of data.

## bar graphs

The data in Table 1.1 shows the average number of tornadoes per year for the ten U.S. cities that have the most tornadoes. The data were averaged over the time period 1950-2007.

## instructional diagrams

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## questions

types of graphs include

``````a) bar graphs.

b) line graphs.

c) circle graphs.

-->  d) all of the above
``````

different types of graph are best suited for representing different types of data.

``````-->  a. true

b. false
``````

## diagram questions

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